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Morgenroth D, McArley T, Khan J, Sandblom E. Mechanisms of enhanced cardiorespiratory performance under hyperoxia differ with exposure duration in yellowtail kingfish. Proc Biol Sci 2024; 291:20232557. [PMID: 38889794 DOI: 10.1098/rspb.2023.2557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 05/06/2024] [Indexed: 06/20/2024] Open
Abstract
Hyperoxia has been shown to expand the aerobic capacity of some fishes, although there have been very few studies examining the underlying mechanisms and how they vary across different exposure durations. Here, we investigated the cardiorespiratory function of yellowtail kingfish (Seriola lalandi) acutely (~20 h) and chronically (3-5 weeks) acclimated to hyperoxia (~200% air saturation). Our results show that the aerobic performance of kingfish is limited in normoxia and increases with environmental hyperoxia. The aerobic scope was elevated in both hyperoxia treatments driven by a ~33% increase in maximum O2 uptake (MO2max), although the mechanisms differed across treatments. Fish acutely transferred to hyperoxia primarily elevated tissue O2 extraction, while increased stroke volume-mediated maximum cardiac output was the main driving factor in chronically acclimated fish. Still, an improved O2 delivery to the heart in chronic hyperoxia was not the only explanatory factor as such. Here, maximum cardiac output only increased in chronic hyperoxia compared with normoxia when plastic ventricular growth occurred, as increased stroke volume was partly enabled by an ~8%-12% larger relative ventricular mass. Our findings suggest that hyperoxia may be used long term to boost cardiorespiratory function potentially rendering fish more resilient to metabolically challenging events and stages in their life cycle.
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Affiliation(s)
- Daniel Morgenroth
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, Gothenburg 405 30, Sweden
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Gothenburg 405 30, Sweden
| | - Tristan McArley
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, Gothenburg 405 30, Sweden
| | - Javed Khan
- National Institute of Water and Atmospheric Research, Northland Marine Research Centre, PO Box 147, Ruakaka 0151, New Zealand
- CH4 Global, 48 Greys Avenue, Auckland 1010, New Zealand
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, Gothenburg 405 30, Sweden
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2
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Haverinen J, Badr A, Korajoki H, Hassinen M, Vornanen M. Dual effect of polyaromatic hydrocarbons on sarco(endo)plasmic reticulum calcium ATPase (SERCA) activity of a teleost fish (Oncorhynchus mykiss). Comp Biochem Physiol C Toxicol Pharmacol 2024; 276:109785. [PMID: 37977241 DOI: 10.1016/j.cbpc.2023.109785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 10/27/2023] [Accepted: 11/08/2023] [Indexed: 11/19/2023]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are embryo- and cardiotoxic to fish that might be associated with improper intracellular Ca2+ management. Since sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) is a major regulator of intracellular Ca2+, the SERCA activity and the contractile properties of rainbow trout (Oncorhynchus mykiss) ventricle were measured in the presence of 3- and 4-cyclic PAHs. In unfractionated ventricular homogenates, acute exposure of SERCA to 0.1-1.0 μM phenanthrene (Phe), retene (Ret), fluoranthene (Flu), or pyrene (Pyr) resulted in concentration-dependent increase in SERCA activity, except for the Flu exposure, with maximal effects of 49.7-83 % at 1 μM. However, PAH mixture did not affect the contractile parameters of trout ventricular strips. Similarly, all PAHs, except Ret, increased the myotomal SERCA activity, but with lower effect (27.8-40.8 % at 1 μM). To investigate the putative chronic effects of PAHs on SERCA, the atp2a2a gene encoding trout cardiac SERCA was expressed in human embryonic kidney (HEK) cells. Culture of HEK cells in the presence of 0.3-1.0 μM Phe, Ret, Flu, and Pyr for 4 days suppressed SERCA expression in a concentration-dependent manner, with maximal inhibition of 49 %, 65 %, 39 % (P < 0.05), and 18 % (P > 0.05), respectively at 1 μM. Current findings indicate divergent effects of submicromolar PAH concentrations on SERCA: stimulation of SERCA activity in acute exposure and inhibition of SERCA expression in chronic exposure. The depressed expression of SERCA is likely to contribute to the embryo- and cardiotoxicity of PAHs by depressing muscle function and altering gene expression.
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Affiliation(s)
- Jaakko Haverinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland.
| | - Ahmed Badr
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland; Zoology Department, Faculty of Science, Sohag University, 82524 Sohag, Egypt
| | - Hanna Korajoki
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland
| | - Minna Hassinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland
| | - Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland
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Schwieterman GD, Hardison EA, Cox GK, Van Wert JC, Birnie-Gauvin K, Eliason EJ. Mechanisms of cardiac collapse at high temperature in a marine teleost (Girella nigrians). Comp Biochem Physiol A Mol Integr Physiol 2023; 286:111512. [PMID: 37726058 DOI: 10.1016/j.cbpa.2023.111512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/11/2023] [Accepted: 09/11/2023] [Indexed: 09/21/2023]
Abstract
Heat-induced mortality in ectotherms may be attributed to impaired cardiac performance, specifically a collapse in maximum heart rate (fHmax), although the physiological mechanisms driving this phenomenon are still unknown. Here, we tested two proposed factors which may restrict cardiac upper thermal limits: noxious venous blood conditions and oxygen limitation. We hypothesized elevated blood [K+] (hyperkalemia) and low oxygen (hypoxia) would reduce cardiac upper thermal limits in a marine teleost (Girella nigricans), while high oxygen (hyperoxia) would increase thermal limits. We also hypothesized higher acclimation temperatures would exacerbate the harmful effects of an oxygen limitation. Using the Arrhenius breakpoint temperature test, we measured fHmax in acutely warmed fish under control (saline injected) and hyperkalemic conditions (elevated plasma [K+]) while exposed to hyperoxia (200% air saturation), normoxia (100% air saturation), or hypoxia (20% air saturation). We also measured ventricle lactate content and venous blood oxygen partial pressure (PO2) to determine if there were universal thresholds in either metric driving cardiac collapse. Elevated [K+] was not significantly correlated with any cardiac thermal tolerance metric. Hypoxia significantly reduced cardiac upper thermal limits (Arrhenius breakpoint temperature [TAB], peak fHmax, temperature of peak heart rate [TPeak], and temperature at arrhythmia [TARR]). Hyperoxia did not alter cardiac thermal limits compared to normoxia. There was no evidence of a species-wide threshold in ventricular [lactate] or venous PO2. Here, we demonstrate that oxygen limits cardiac thermal tolerance only in instances of hypoxia, but that other physiological processes are responsible for causing temperature-induced heart failure when oxygen is not limited.
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Affiliation(s)
- Gail D Schwieterman
- Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA; School of Marine Sciences, University of Maine, Orono, ME, USA; Maine Agricultural and Forest Experiment Station, Orono, ME, USA.
| | - Emily A Hardison
- Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA. https://twitter.com/eahardison
| | | | - Jacey C Van Wert
- Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA. https://twitter.com/jacey_van_wert
| | - Kim Birnie-Gauvin
- Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA; Section for Freshwater Fisheries and Ecology, National Institute of Aquatic Resources, Technical University of Denmark, Silkeborg, Denmark. https://twitter.com/kbg_conserv
| | - Erika J Eliason
- Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA
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Ferro LA, Fernandes SLA, Kalinin AL, Monteiro DA. Effects of exposure to sediment-associated fipronil on cardiac function of Neotropical armored catfish Hypostomus regani. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2023; 58:236-245. [PMID: 36803268 DOI: 10.1080/10934529.2023.2182582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 02/13/2023] [Accepted: 02/15/2023] [Indexed: 06/18/2023]
Abstract
Fipronil is widely used as a broad-spectrum insecticide in agriculture, urban environments, and veterinary medicine. Fipronil can enter aquatic ecosystems and spread to sediment and organic matter, representing a risk to non-target species. This study aimed to evaluate the effects of short-term (96 h) exposure to a low and realistic concentration of sediment-associated fipronil (4.2 µg.kg-1 of Regent® 800 WG) on myocardial contractility of armored catfish Hypostomus regain, a benthic fish species. Fipronil exposure induced increased inotropism and acceleration of contractile kinetics, although no alterations in the relative ventricular mass were observed. This better cardiac function was associated with an elevated expression and/or function of the Na+/Ca2+ exchanger and its marked contribution to contraction and relaxation, probably due to a stress-induced adrenergic stimulation. Ventricle strips of exposed fish also exhibited a faster relaxation and a higher cardiac pumping capacity, indicating that armored catfish were able to perform cardiac adjustments to face the exposure. However, a high energetic cost to maintain an increased cardiac performance can make fish more susceptible to other stressors, impairing developmental processes and/or survival. These findings highlight the need for regulations of emerging contaminants, such as fipronil, to ensure adequate protection of the aquatic system.
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Affiliation(s)
- Lucas Abreu Ferro
- Joint Graduate Program in Physiological Sciences, Federal University of São Carlos (UFSCar), São Paulo State University (UNESP), São Carlos, Araraquara, Brazil
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
| | - Suzana Luisa Alves Fernandes
- Joint Graduate Program in Physiological Sciences, Federal University of São Carlos (UFSCar), São Paulo State University (UNESP), São Carlos, Araraquara, Brazil
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
| | - Ana Lúcia Kalinin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
| | - Diana Amaral Monteiro
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
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Cerra MC, Filice M, Caferro A, Mazza R, Gattuso A, Imbrogno S. Cardiac Hypoxia Tolerance in Fish: From Functional Responses to Cell Signals. Int J Mol Sci 2023; 24:ijms24021460. [PMID: 36674975 PMCID: PMC9866870 DOI: 10.3390/ijms24021460] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 01/09/2023] [Accepted: 01/10/2023] [Indexed: 01/14/2023] Open
Abstract
Aquatic animals are increasingly challenged by O2 fluctuations as a result of global warming, as well as eutrophication processes. Teleost fish show important species-specific adaptability to O2 deprivation, moving from intolerance to a full tolerance of hypoxia and even anoxia. An example is provided by members of Cyprinidae which includes species that are amongst the most tolerant hypoxia/anoxia teleosts. Living at low water O2 requires the mandatory preservation of the cardiac function to support the metabolic and hemodynamic requirements of organ and tissues which sustain whole organism performance. A number of orchestrated events, from metabolism to behavior, converge to shape the heart response to the restricted availability of the gas, also limiting the potential damages for cells and tissues. In cyprinids, the heart is extraordinarily able to activate peculiar strategies of functional preservation. Accordingly, by using these teleosts as models of tolerance to low O2, we will synthesize and discuss literature data to describe the functional changes, and the major molecular events that allow the heart of these fish to sustain adaptability to O2 deprivation. By crossing the boundaries of basic research and environmental physiology, this information may be of interest also in a translational perspective, and in the context of conservative physiology, in which the output of the research is applicable to environmental management and decision making.
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Muir CA, Garner SR, Damjanovski S, Neff BD. Temperature-dependent plasticity mediates heart morphology and thermal performance of cardiac function in juvenile Atlantic salmon (Salmo salar). J Exp Biol 2022; 225:276049. [PMID: 35860948 DOI: 10.1242/jeb.244305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 07/08/2022] [Indexed: 11/20/2022]
Abstract
In many fishes, upper thermal tolerance is thought to be limited in part by the heart's ability to meet increased oxygen demands during periods of high temperature. Temperature-dependent plasticity within the cardiovascular system may help fishes cope with the thermal stress imposed by increasing water temperatures. In this study, we examined plasticity in heart morphology and function in juvenile Atlantic salmon (Salmo salar) reared under control (+0°C) or elevated (+4°C) temperatures. Using noninvasive Doppler echocardiography, we measured the effect of acute warming on maximum heart rate, stroke distance, and derived cardiac output. A 4°C increase in average developmental temperature resulted in a>5°C increase in the Arrhenius breakpoint temperature for maximum heart rate and enabled the hearts of these fish to continue beating rhythmically to temperatures approximately 2°C higher than control fish. However, these differences in thermal performance were not associated with plasticity in maximum cardiovascular capacity, as peak measures of heart rate, stroke distance, and derived cardiac output did not differ between temperature treatments. Histological analysis of the heart revealed that while ventricular roundness and relative ventricle size did not differ between treatments, the proportion of compact myocardium in the ventricular wall was significantly greater in fish raised at elevated temperatures. Our findings contribute to the growing understanding of how the thermal environment can affect phenotypes later in life and identifies a morphological strategy that may help fishes cope with acute thermal stress.
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Affiliation(s)
- Carlie A Muir
- Department of Biology, Western University, London, ON, Canada
| | - Shawn R Garner
- Department of Biology, Western University, London, ON, Canada
| | | | - Bryan D Neff
- Department of Biology, Western University, London, ON, Canada
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Pettinau L, Lancien F, Zhang Y, Mauduit F, Ollivier H, Farrell AP, Claireaux G, Anttila K. Warm, but not hypoxic acclimation, prolongs ventricular diastole and decreases the protein level of Na +/Ca 2+ exchanger to enhance cardiac thermal tolerance in European sea bass. Comp Biochem Physiol A Mol Integr Physiol 2022; 272:111266. [PMID: 35772648 DOI: 10.1016/j.cbpa.2022.111266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Revised: 06/24/2022] [Accepted: 06/24/2022] [Indexed: 10/17/2022]
Abstract
One of the physiological mechanisms that can limit the fish's ability to face hypoxia or elevated temperature, is maximal cardiac performance. Yet, few studies have measured how cardiac electrical activity and associated calcium cycling proteins change with acclimation to those environmental stressors. To examine this, we acclimated European sea bass for 6 weeks to three experimental conditions: a seasonal average temperature in normoxia (16 °C; 100% air sat.), an elevated temperature in normoxia (25 °C; 100% air sat.) and a seasonal average temperature in hypoxia (16 °C; 50% air sat.). Following each acclimation, the electrocardiogram was measured to assess how acclimation affected the different phases of cardiac cycle, the maximal heart rate (fHmax) and cardiac thermal performance during an acute increase of temperature. Whereas warm acclimation prolonged especially the diastolic phase of the ventricular contraction, reduced the fHmax and increased the cardiac arrhythmia temperature (TARR), hypoxic acclimation was without effect on these functional indices. We measured the level of two key proteins involved with cellular relaxation of cardiomyocytes, i.e. sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) and Na+/Ca2+ exchanger (NCX). Warm acclimation reduced protein level of both NCX and SERCA and hypoxic acclimation reduced SERCA protein levels without affecting NCX. The changes in ventricular NCX level correlated with the observed changes in diastole duration and fHmax as well as TARR. Our results shed new light on mechanisms of cardiac plasticity to environmental stressors and suggest that NCX might be involved with the observed functional changes, yet future studies should also measure its electrophysiological activity.
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Affiliation(s)
- Luca Pettinau
- Department of Biology, University of Turku, 20014 Turku, Finland.
| | - Frédéric Lancien
- Université de Bretagne Occidentale, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, France
| | - Yangfan Zhang
- Department of Zoology, Faculty of Land and Food System, University of British Columbia, Vancouver, British Columbia, Canada. https://twitter.com/theYangfanZHANG
| | - Florian Mauduit
- Université de Bretagne Occidentale, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, France
| | - Hélène Ollivier
- Université de Bretagne Occidentale, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, France
| | - Anthony P Farrell
- Department of Zoology, Faculty of Land and Food System, University of British Columbia, Vancouver, British Columbia, Canada
| | - Guy Claireaux
- Université de Bretagne Occidentale, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, France
| | - Katja Anttila
- Department of Biology, University of Turku, 20014 Turku, Finland. https://twitter.com/anttilaLab
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Joyce W, Wang T. Regulation of heart rate in vertebrates during hypoxia: A comparative overview. Acta Physiol (Oxf) 2022; 234:e13779. [PMID: 34995393 DOI: 10.1111/apha.13779] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 11/12/2021] [Accepted: 01/01/2022] [Indexed: 12/18/2022]
Abstract
Acute exposure to low oxygen (hypoxia) places conflicting demands on the heart. Whilst an increase in heart rate (tachycardia) may compensate systemic oxygen delivery as arterial oxygenation falls, the heart itself is an energetically expensive organ that may benefit from slowing (bradycardia) to reduce work when oxygen is limited. Both strategies are apparent in vertebrates, with tetrapods (mammals, birds, reptiles, and amphibians) classically exhibiting hypoxic tachycardia and fishes displaying characteristic hypoxic bradycardia. With a richer understanding of the ontogeny and evolution of the responses, however, we see similarities in the underlying mechanisms between vertebrate groups. For example, in adult mammals, primary bradycardia results from the hypoxic stimulation of carotid body chemoreceptors that are overwhelmed by mechano-sensory feedback from the lung associated with hyperpnoea. Fish-like bradycardia prevails in the mammalian foetus (which, at this stage, is incapable of pulmonary ventilation), and in fish and foetus alike, the bradycardia ensues despite an elevation of circulating catecholamines. In both cases, the reduced heart rate may primarily serve to protect the heart. Thus, the comparative perspective offers fundamental insight into how and why different vertebrates regulate heart rate in different ways during periods of hypoxia.
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Affiliation(s)
- William Joyce
- Department of Biology—Zoophysiology Aarhus University Aarhus C Denmark
| | - Tobias Wang
- Department of Biology—Zoophysiology Aarhus University Aarhus C Denmark
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Smith B, Crossley DA, Wang T, Joyce W. No evidence for pericardial restraint in the snapping turtle (Chelydra serpentina) following pharmacologically-induced bradycardia at rest or during exercise. Am J Physiol Regul Integr Comp Physiol 2022; 322:R389-R399. [PMID: 35200048 PMCID: PMC9018006 DOI: 10.1152/ajpregu.00004.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Most animals elevate cardiac output during exercise through a rise in heart rate (fH), whilst stroke volume (VS) remains relatively unchanged. Cardiac pacing reveals that elevating fH alone does not alter cardiac output, which is instead largely regulated by the peripheral vasculature. In terms of myocardial oxygen demand, an increase in fH is more costly than that which would incur if VS instead were to increase. We hypothesized that fH must increase because any substantial rise in VS would be constrained by the pericardium. To investigate this hypothesis, we explored the effects of pharmacologically-induced bradycardia, with ivabradine treatment, on VS at rest and during exercise in the common snapping turtle (Chelydra serpentina) with intact or opened pericardium. We first showed that, in isolated myocardial preparations, ivabradine exerted a pronounced positive inotropic effect on atrial tissue, but only minor effects on ventricle. Ivabradine reduced fH in vivo, such that exercise tachycardia was attenuated. Pulmonary and systemic VS rose in response to ivabradine. The rise in pulmonary VS largely compensated for the bradycardia at rest, leaving total pulmonary flow unchanged by ivabradine, although ivabradine reduced pulmonary blood flow during swimming (exercise x ivabradine interaction, P<0.05). Although systemic VS increased, systemic blood flow was reduced by ivabradine both at rest and during exercise, in spite of ivabradine's potential to increase cardiac contractility. Opening the pericardium had no effect on fH, VS or blood flows before or after ivabradine, indicating that the pericardium does not constrain VS in turtles, even during pharmacologically-induced bradycardia.
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Affiliation(s)
- Brandt Smith
- Department of Biological Sciences, University of North Texas, Denton, TX, United States
| | - Dane A Crossley
- Department of Biological Sciences, University of North Texas, Denton, TX, United States
| | - Tobias Wang
- Department of Biology- Zoophysiology, Aarhus University, Aarhus C, Denmark
| | - William Joyce
- Department of Biology- Zoophysiology, Aarhus University, Aarhus C, Denmark
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Monteiro DA, Lopes AG, Jejcic NU, da Silva Vasconcelos E, Kalinin AL, Rantin FT. Cardiac contractility of the African sharptooth catfish, Clarias gariepinus: role of extracellular Ca 2+, sarcoplasmic reticulum, and β-adrenergic stimulation. FISH PHYSIOLOGY AND BIOCHEMISTRY 2021; 47:1969-1982. [PMID: 34668117 DOI: 10.1007/s10695-021-01023-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 10/07/2021] [Indexed: 06/13/2023]
Abstract
This study investigated the dependence of contraction from extracellular Ca2+, the presence of a functional sarcoplasmic reticulum (SR), and the effects of β-adrenergic stimulation using isometric cardiac muscle preparations. Moreover, the expression of Ca2+-handling proteins such as SR-Ca2+-ATPase (SERCA), phospholamban (PLN), and Na+/Ca2+ exchanger (NCX) were also evaluated in the ventricular tissue of adult African sharptooth catfish, Clarias gariepinus, a facultative air-breathing fish. In summary, we observed that (1) contractility was strongly regulated by extracellular Ca2+; (2) inhibition of SR Ca2+-release by application of ryanodine reduced steady-state force production; (3) ventricular myocardium exhibited clear post-rest decay, even in the presence of ryanodine, indicating a decrease in SR Ca2+ content and NCX as the main pathway for Ca2+ extrusion; (4) a positive force-frequency relationship was observed above 60 bpm (1.0 Hz); (5) ventricular tissue was responsive to β-adrenergic stimulation, which caused significant increases in twitch force, kept a linear force-frequency relationship from 12 to 96 bpm (0.2 to Hz), and improved the cardiac pumping capacity (CPC); and (6) African catfish myocardium exhibited similar expression patterns of NCX, SERCA, and PLN, corroborating our findings that both mechanisms for Ca2+ transport across the SR and sarcolemma contribute to Ca2+ activator. In conclusion, this fish species displays great physiological plasticity of E-C coupling, able to improve the ability to maintain cardiac performance under physiological conditions to ecological and/or adverse environmental conditions, such as hypoxic air-breathing activity.
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Affiliation(s)
- Diana Amaral Monteiro
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil.
| | - André Guelli Lopes
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
- Joint Graduate Program in Physiological Sciences, Federal University of São Carlos - UFSCar/São Paulo State University, UNESP Campus Araraquara, São Paulo, Brazil
| | - Nathalia Usun Jejcic
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
| | - Eliton da Silva Vasconcelos
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
- Joint Graduate Program in Physiological Sciences, Federal University of São Carlos - UFSCar/São Paulo State University, UNESP Campus Araraquara, São Paulo, Brazil
| | - Ana Lúcia Kalinin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
| | - Francisco Tadeu Rantin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
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11
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Gates MA, Morash AJ, Lamarre SG, MacCormack TJ. Intracellular taurine deficiency impairs cardiac contractility in rainbow trout (Oncorhynchus mykiss) without affecting aerobic performance. J Comp Physiol B 2021; 192:49-60. [PMID: 34581858 DOI: 10.1007/s00360-021-01407-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 09/03/2021] [Accepted: 09/16/2021] [Indexed: 01/07/2023]
Abstract
Taurine is a non-proteinogenic sulfonic acid found in high concentrations inside vertebrate cardiomyocytes and its movement across the sarcolemmal membrane is critical for cell volume regulation. Taurine deficiency is rare in mammals, where it impairs cardiac contractility and leads to congestive heart failure. In fish, cardiac taurine levels vary substantially between species and can decrease by up to 60% in response to environmental change but its contribution to cardiac function is understudied. We addressed this gap in knowledge by generating a taurine-deficient rainbow trout (Oncorhynchus mykiss) model using a feed enriched with 3% β-alanine to inhibit cellular taurine uptake. Cardiac taurine was reduced by 17% after 4 weeks with no effect on growth or condition factor. Taurine deficiency did not affect routine or maximum rates of O2 consumption, aerobic scope, or critical swimming speed in whole animals but cardiac contractility was significantly impaired. In isometrically contracting ventricular strip preparations, the force-frequency and extracellular Ca2+-sensitivity relationships were both shifted downward and maximum pacing frequency was significantly lower in β-alanine fed trout. Cardiac taurine deficiency reduces sarcoplasmic reticular Ca2+-ATPase activity in mammals and our results are consistent with such an effect in rainbow trout. Our data indicate that intracellular taurine contributes to the regulation of cardiac contractility in rainbow trout. Aerobic performance was unaffected in β-alanine-fed animals, but further study is needed to determine if more significant natural reductions in taurine may constrain performance under certain environmental conditions.
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Affiliation(s)
- M A Gates
- Department of Chemistry and Biochemistry, Mount Allison University, 63C York St., Sackville, NB, E4L1G8, Canada.,Department of Biology, Mount Allison University, Sackville, NB, Canada.,Department of Biology, Université de Moncton, Moncton, NB, Canada
| | - A J Morash
- Department of Chemistry and Biochemistry, Mount Allison University, 63C York St., Sackville, NB, E4L1G8, Canada.,Department of Biology, Mount Allison University, Sackville, NB, Canada.,Department of Biology, Université de Moncton, Moncton, NB, Canada
| | - S G Lamarre
- Department of Chemistry and Biochemistry, Mount Allison University, 63C York St., Sackville, NB, E4L1G8, Canada.,Department of Biology, Mount Allison University, Sackville, NB, Canada.,Department of Biology, Université de Moncton, Moncton, NB, Canada
| | - T J MacCormack
- Department of Chemistry and Biochemistry, Mount Allison University, 63C York St., Sackville, NB, E4L1G8, Canada. .,Department of Biology, Mount Allison University, Sackville, NB, Canada. .,Department of Biology, Université de Moncton, Moncton, NB, Canada.
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12
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Muir CA, Neff BD, Damjanovski S. Adaptation of a mouse Doppler echocardiograph system for assessing cardiac function and thermal performance in a juvenile salmonid. CONSERVATION PHYSIOLOGY 2021; 9:coab070. [PMID: 34512992 PMCID: PMC8415535 DOI: 10.1093/conphys/coab070] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 06/04/2021] [Accepted: 08/11/2021] [Indexed: 06/13/2023]
Abstract
Measures of cardiac performance are pertinent to the study of thermal physiology and exercise in teleosts, particularly as they pertain to migration success. Increased heart rate, stroke volume and cardiac output have previously been linked to improved swimming performance and increased upper thermal tolerance in anadromous salmonids. To assess thermal performance in fishes, it has become commonplace to measure the response of maximum heart rate to warming using electrocardiograms. However, electrocardiograms do not provide insight into the hemodynamic characteristics of heart function that can impact whole-animal performance. Doppler echocardiography is a popular tool used to examine live animal processes, including real-time cardiac function. This method allows for nonsurgical measurements of blood flow velocity through the heart and has been used to detect abnormalities in cardiovascular function, particularly in mammals. Here, we show how a mouse Doppler echocardiograph system can be adapted for use in a juvenile salmonid over a range of temperatures and timeframes. Using this compact, noninvasive system, we measured maximum heart rate, atrioventricular (AV) blood flow velocity, the early flow-atrial flow ratio and stroke distance in juvenile Atlantic salmon (Salmo salar) during acute warming. Using histologically determined measures of AV valve area, we show how stroke distance measurements obtained with this system can be used to calculate ventricular inflow volume and approximate cardiac output. Further, we show how this Doppler system can be used to determine cardiorespiratory thresholds for thermal performance, which are increasingly being used to predict the consequences that warming water temperatures will have on migratory fishes.
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Affiliation(s)
- Carlie A Muir
- Department of Biology, Western University, London, Ontario, Canada N6A 5B7
| | - Bryan D Neff
- Department of Biology, Western University, London, Ontario, Canada N6A 5B7
| | - Sashko Damjanovski
- Department of Biology, Western University, London, Ontario, Canada N6A 5B7
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13
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Kibler NA, Nuzhny VP, Kharin SN, Shmakov DN. Effect of atrial artificial electrical stimulation on depolarization and repolarization and hemodynamics of the heart ventricle in rainbow trout Oncorhynchus mykiss. FISH PHYSIOLOGY AND BIOCHEMISTRY 2021; 47:1329-1339. [PMID: 34241764 DOI: 10.1007/s10695-021-00983-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 06/25/2021] [Indexed: 06/13/2023]
Abstract
The spatial-temporal organization of the activation, repolarization and hemodynamics of the heart ventricle in rainbow trout, Oncorhynchus mykiss, adapted to a temperature of 5-7 °C, were studied from the normal sinus rhythm (21.6 ± 4.9 bpm) to the highest possible heart rhythm (HR) (60 bpm), during which deterioration of the contractile activity of the myocardium occurred. Regardless of the HR, the main pattern of excitation of the heart ventricle was the movement of the depolarization wave from the dorsal areas of the base in the base-apical and ventral directions with the capture of the entire thickness of the walls, with a slight difference in the time of activation of the subendocardium compared to the subepicardium. The increase in HR above the sinus rhythm caused significant shortening of local repolarization durations in all areas and layers (endocardial, intramural and subepicardial) of the heart ventricle. Changes in local durations of repolarization led to an increase in the heterogeneity of repolarization of the ventricular myocardium; as a result, a deterioration of its contractility was observed. In relation to the sinus rhythm, the maximal systolic pressure in the heart ventricle decreased, the diastolic and end-diastolic pressure increased, and the maximum rates of pressure rise and fall decreased. In rainbow trout adapted to a temperature of 5-7 °C at sinus rhythm, the pumping function of the heart was probably within the upper limit of the physiological norm, and a further increase in the heart rate led to a decline in myocardial contractility.
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Affiliation(s)
- Natalya A Kibler
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia.
| | - Vladimir P Nuzhny
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia
| | - Sergey N Kharin
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia
| | - Dmitry N Shmakov
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia
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14
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Morgenroth D, McArley T, Gräns A, Axelsson M, Sandblom E, Ekström A. Coronary blood flow influences tolerance to environmental extremes in fish. J Exp Biol 2021; 224:jeb.239970. [PMID: 33688058 DOI: 10.1242/jeb.239970] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 03/03/2021] [Indexed: 12/16/2022]
Abstract
Approximately half of all fishes have, in addition to the luminal venous O2 supply, a coronary circulation supplying the heart with fully oxygenated blood. Yet, it is not fully understood how coronary O2 delivery affects tolerance to environmental extremes such as warming and hypoxia. Hypoxia reduces arterial oxygenation, while warming increases overall tissue O2 demand. Thus, as both stressors are associated with reduced venous O2 supply to the heart, we hypothesised that coronary flow benefits hypoxia and warming tolerance. To test this hypothesis, we blocked coronary blood flow (via surgical coronary ligation) in rainbow trout (Oncorhynchus mykiss) and assessed how in vivo cardiorespiratory performance and whole-animal tolerance to acute hypoxia and warming was affected. While coronary ligation reduced routine stroke volume relative to trout with intact coronaries, cardiac output was maintained by an increase in heart rate. However, in hypoxia, coronary-ligated trout were unable to increase stroke volume to maintain cardiac output when bradycardia developed, which was associated with a slightly reduced hypoxia tolerance. Moreover, during acute warming, coronary ligation caused cardiac function to collapse at lower temperatures and reduced overall heat tolerance relative to trout with intact coronary arteries. We also found a positive relationship between individual hypoxia and heat tolerance across treatment groups, and tolerance to both environmental stressors was positively correlated with cardiac performance. Collectively, our findings show that coronary perfusion improves cardiac O2 supply and therefore cardiovascular function at environmental extremes, which benefits tolerance to natural and anthropogenically induced environmental perturbations.
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Affiliation(s)
- Daniel Morgenroth
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| | - Tristan McArley
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| | - Albin Gräns
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, 532 23 Skara, Sweden
| | - Michael Axelsson
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| | - Andreas Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
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15
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Lopes AG, Monteiro DA, Kalinin AL. Effects of change in temperature on the cardiac contractility of broad-snouted caiman (Caiman latirostris) during digestion. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2021; 335:417-425. [PMID: 33773091 DOI: 10.1002/jez.2457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 03/12/2021] [Accepted: 03/13/2021] [Indexed: 11/07/2022]
Abstract
In many reptiles, digestion has been associated with the selection of higher body temperatures, the so-called post-prandial thermophilic response. This study aimed to investigate the excitation-contraction (E-C) coupling in postprandial broad-snouted caimans (Caiman latirostris) in response to acute warming within a preferred body temperature range of crocodiles. Isometric preparations subjected to a temperature transition from 25°C to 30°C were used to investigate myocardial contractility of postprandial caimans, that is, 48 h after the animals ingested a rodent meal corresponding to 15% of body mass. The caiman heart exhibits a negative force-frequency relationship that is independent of the temperature. At 25°C, cardiac muscle was able to maintain a constant force up to 36 bpm, above which it decreased significantly, reaching minimum values at the highest frequency of 84 bpm. Moreover, E-C coupling is predominantly dependent on transsarcolemmal Ca2+ transport denoted by the lack of significant ryanodine effects on force generation. On the contrary, ventricular strips at 30°C were able to sustain the cardiac contractility at higher pacing frequencies (from 12 to 144 bpm) due to an important role of Na+ /Ca2+ exchanger in Ca2+ cycling, as indicated by the decay of the post-rest contraction, and a significant contribution of the sarcoplasmic reticulum above 72 bpm. Our results demonstrated that the myocardium of postprandial caimans exhibits a significant degree of thermal plasticity of E-C coupling during acute warming. Therefore, myocardial contractility can be maximized when postprandial broad-snouted caimans select higher body temperatures (preferred temperature zone) following feeding.
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Affiliation(s)
- André G Lopes
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil.,Joint Graduate Program in Physiological Sciences, Federal University of São Carlos-UFSCar/São Paulo State University, UNESP Campus Araraquara, Araraquara, São Paulo, Brazil
| | - Diana A Monteiro
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
| | - Ana L Kalinin
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
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16
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The effects of elevated potassium, acidosis, reduced oxygen levels, and temperature on the functional properties of isolated myocardium from three elasmobranch fishes: clearnose skate (Rostroraja eglanteria), smooth dogfish (Mustelus canis), and sandbar shark (Carcharhinus plumbeus). J Comp Physiol B 2021; 191:127-141. [PMID: 33394123 DOI: 10.1007/s00360-020-01328-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 10/27/2020] [Accepted: 11/15/2020] [Indexed: 10/22/2022]
Abstract
Elevated plasma potassium levels (hyperkalemia), reduced plasma pH (acidosis), reduced blood oxygen content, and elevated temperatures are associated with species-specific rates of at-vessel and post-release mortality in elasmobranch fishes. The mechanism linking these physiological disturbances to mortality remains undetermined however, and we hypothesize that the proximate cause is reduced myocardial function. We measured changes in the functional properties of isolated ventricular myocardial strips from clearnose skate (Rostroraja eglanteria), smooth dogfish (Mustelus canis), and sandbar shark (Carcharhinus plumbeus) when subjected to the following stressors (both in isolation and in combination): hyperkalemia (7.4 mM K+), acidosis (from 7.9 to 7.1), and reduced oxygen (to 31% O2 saturation) applied at temperatures 5 °C above and below holding temperatures. We selected these species based on phylogenetic distance, diverse routine activity levels, and their tolerance to capture and transport. Stressors had a few significant species-specific detrimental impacts on myocardial function (e.g., a 33-45% decrease in net force under acidosis + low O2). Net force production of myocardial strips from clearnose skate and smooth dogfish approximately doubled following exposure to isoproterenol, demonstrating that these species possess beta-adrenergic receptors and that their stimulation could provide a mechanism for preservation of cardiac function during stress. Our results suggest that disruption of physiological homeostasis associated with capture may fatally impair cardiac function in some elasmobranch species, although research with more severe stressors is needed.
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17
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Goulding AT, Farrell AP. The effect of temperature acclimation on the force-frequency relationship and adrenergic sensitivity of the ventricle of two populations of juvenile sockeye salmon. J Comp Physiol B 2020; 190:717-730. [PMID: 32770260 DOI: 10.1007/s00360-020-01299-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 06/08/2020] [Accepted: 07/15/2020] [Indexed: 11/26/2022]
Abstract
We tested the hypothesis that cardiorespiratory differences known to exist among adult sockeye salmon populations also exist in the juveniles. To test this hypothesis, we compared cardiac contractility and adrenergic responsiveness of juvenile sockeye salmon from two geographically isolated populations that were reared from eggs under common garden conditions and at two acclimation temperatures (5 °C and 14 °C). However, we found no substantive differences in the force-frequency response (FFR) and the cardiac pumping capacity of juveniles from Weaver Creek and Chilko River populations, even when we considered wild-reared juveniles from one of the populations. An unexpected discovery for all fish groups at 5 °C was a rather flat FFR during tonic β-adrenergic stimulation (βAR) stimulation. Curiously, while active tension nearly doubled with maximum βAR stimulation at low pacing frequencies for all fish groups, a negative FFR with maximum βAR stimulation meant that this inotropic benefit was lost at the highest pacing frequency (0.8 Hz). Active tension with tonic βAR stimulation was similar at 14 °C, but maximum pacing frequency doubled and all fish groups displayed a modest negative FFR. Maximum βAR stimulation again doubled active tension and this benefit was retained even at the highest pacing frequency (1.6 Hz) at 14 °C. Even though subtle population differences were apparent for the FFR and pumping capacity, their biological significance is unclear. What is clear, however, is that the cardiac pumping capacity of juvenile sockeye would benefit more from βAR stimulation swimming at 15 °C than when swimming at 5 °C.
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Affiliation(s)
- A T Goulding
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada.
| | - A P Farrell
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada
- Faculty of Land and Food Systems, University of British Columbia, 2357 Main Mall, Vancouver, BC, V6T 1Z4, Canada
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18
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Abstract
In the 1950s, Arthur C. Guyton removed the heart from its pedestal in cardiovascular physiology by arguing that cardiac output is primarily regulated by the peripheral vasculature. This is counterintuitive, as modulating heart rate would appear to be the most obvious means of regulating cardiac output. In this Review, we visit recent and classic advances in comparative physiology in light of this concept. Although most vertebrates increase heart rate when oxygen demands rise (e.g. during activity or warming), experimental evidence suggests that this tachycardia is neither necessary nor sufficient to drive a change in cardiac output (i.e. systemic blood flow, Q̇ sys) under most circumstances. Instead, Q̇ sys is determined by the interplay between vascular conductance (resistance) and capacitance (which is mainly determined by the venous circulation), with a limited and variable contribution from heart function (myocardial inotropy). This pattern prevails across vertebrates; however, we also highlight the unique adaptations that have evolved in certain vertebrate groups to regulate venous return during diving bradycardia (i.e. inferior caval sphincters in diving mammals and atrial smooth muscle in turtles). Going forward, future investigation of cardiovascular responses to altered metabolic rate should pay equal consideration to the factors influencing venous return and cardiac filling as to the factors dictating cardiac function and heart rate.
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Affiliation(s)
- William Joyce
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark .,Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON K1N 6N5, Canada
| | - Tobias Wang
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark
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19
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Ainerua MO, Tinwell J, Kompella SN, Sørhus E, White KN, van Dongen BE, Shiels HA. Understanding the cardiac toxicity of the anthropogenic pollutant phenanthrene on the freshwater indicator species, the brown trout (Salmo trutta): From whole heart to cardiomyocytes. CHEMOSPHERE 2020; 239:124608. [PMID: 31499312 PMCID: PMC6857438 DOI: 10.1016/j.chemosphere.2019.124608] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 08/15/2019] [Accepted: 08/17/2019] [Indexed: 05/05/2023]
Abstract
Freshwater systems are faced with a myriad of stressors including geomorphological alterations, nutrient overloading and pollution. Previous studies in marine fish showed polyaromatic hydrocarbons (PAHs) to be cardiotoxic. However, the cardiotoxicity of anthropogenic pollutants in freshwater fishes is unclear and has not been examined across multiple levels of cardiac organization. Here we investigated the effect of phenanthrene (Phe), a pervasive anthropogenic pollutant on a sentinel freshwater species, the brown trout (Salmo trutta). We first examined the electrical activity of the whole heart and found prolongation (∼8.6%) of the QT interval (time between ventricular depolarization and repolarization) of the electrocardiogram (ECG) and prolongation (∼13.2%) of the monophasic action potential duration (MAPD) following ascending doses of Phe. At the tissue level, Phe significantly reduced trabecular force generation by ∼24% at concentration 15 μM and above, suggesting Phe reduces cellular calcium cycling. This finding was supported by florescent microscopy showing a reduction (∼39%) in the intracellular calcium transient amplitude following Phe exposure in isolated brown trout ventricular myocytes. Single-cell electrophysiology was used to reveal the mechanism underlying contractile and electrical dysfunction following Phe exposure. A Phe-dependent reduction (∼38%) in the L-type Ca2+ current accounts, at least in part, for the lowered Ca2+ transient and force production. Prolongation of the MAPD and QT interval was explained by a reduction (∼70%) in the repolarising delayed rectifier K+ current following Phe exposure. Taken together, our study shows a direct impact of Phe across multiple levels of cardiac organization in a key freshwater salmonid.
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Affiliation(s)
- Martins Oshioriamhe Ainerua
- Cardiovascular Division, School of Medicine, Faculty of Biology, Medicine and Health, University of Manchester, Core Technology Facility Building, Manchester, M13 9NT, United Kingdom; Department of Animal and Environmental Biology, Faculty of Life Sciences, University of Benin, PMB 1154, Benin City, Nigeria
| | - Jake Tinwell
- Cardiovascular Division, School of Medicine, Faculty of Biology, Medicine and Health, University of Manchester, Core Technology Facility Building, Manchester, M13 9NT, United Kingdom
| | - Shiva Nag Kompella
- Cardiovascular Division, School of Medicine, Faculty of Biology, Medicine and Health, University of Manchester, Core Technology Facility Building, Manchester, M13 9NT, United Kingdom
| | - Elin Sørhus
- Institute of Marine Research, P.O. Box 1870, Nordnes, NO-5817, Bergen, Norway
| | - Keith N White
- School of Earth Atmospheric and Environmental Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9GB, United Kingdom
| | - Bart E van Dongen
- School of Earth Atmospheric and Environmental Sciences, Williamson Research Centre for Molecular Science, University of Manchester, Williamson Building, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Holly A Shiels
- Cardiovascular Division, School of Medicine, Faculty of Biology, Medicine and Health, University of Manchester, Core Technology Facility Building, Manchester, M13 9NT, United Kingdom.
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20
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Abramochkin DV, Matchkov V, Wang T. A characterization of the electrophysiological properties of the cardiomyocytes from ventricle, atrium and sinus venosus of the snake heart. J Comp Physiol B 2019; 190:63-73. [DOI: 10.1007/s00360-019-01253-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/15/2019] [Accepted: 12/08/2019] [Indexed: 12/21/2022]
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21
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Kubly KL, Stecyk JAW. Contractile performance of the Alaska blackfish (Dallia pectoralis) ventricle: Assessment of the effects of temperature, pacing frequency, the role of the sarcoplasmic reticulum in contraction and adrenergic stimulation. Comp Biochem Physiol A Mol Integr Physiol 2019; 238:110564. [PMID: 31493554 DOI: 10.1016/j.cbpa.2019.110564] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 08/24/2019] [Accepted: 08/29/2019] [Indexed: 12/29/2022]
Abstract
The air-breathing Alaska blackfish (Dallia pectoralis) experiences aquatic hypoxia, but restricted air-access in winter due to ice-cover. To lend insight into its overwintering strategy, we examined the effects of thermal acclimation (15 °C vs. 5 °C), acute temperature change (to 10 °C), increased pacing frequency, inhibition of sarcoplasmic reticulum (SR) Ca2+ release and uptake and adrenaline (1000 nmol l-1) on the contractile performance of isometrically-contracting, electrically-paced ventricular strips. At routine pacing frequencies, maximal developed force (Fmax) was equivalent at 5 °C (2.1 ± 0.2 mN mm-2) and 15 °C (2.2 ± 0.3 mN mm-2), whereas contraction durations were 2.2- to 2.4-times longer and contraction rates 2.4- to 3.5-times slower at 5 °C. Maximum contraction frequency was reduced by decreased temperature, being 0.91 ± 0.04 Hz at 15 °C, 0.35 ± 0.02 Hz at 5 °C and equivalent between acclimation groups at 10 °C (~0.8 Hz). 15 °C and 5 °C strips were insensitive to SR inhibition at routine stimulation frequencies, but SR function supported high contraction rates at 10 °C and 15 °C. Adrenaline shortened T0.5R and increased relaxation rate by 18-40% at 15 °C, whereas at 5 °C, adrenaline augmented Fmax by 15-25%, in addition to increasing contraction kinetics by 22-82% and decreasing contraction duration by 20%. Overall, the results reveal that ventricular contractility is suppressed in cold-acclimated Alaska blackfish largely by acute and perhaps direct effects of decreased temperature, which effectively preconditions the tissue for low energy supply during winter hypoxia. Additionally, the level of cardiac performance associated with maintained activity in winter is supported by enhanced inotropic responsiveness to adrenaline at 5 °C.
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Affiliation(s)
- Kerry L Kubly
- Department of Biological Sciences, University of Alaska Anchorage, AK, United States
| | - Jonathan A W Stecyk
- Department of Biological Sciences, University of Alaska Anchorage, AK, United States.
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22
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Heuer RM, Galli GLJ, Shiels HA, Fieber LA, Cox GK, Mager EM, Stieglitz JD, Benetti DD, Grosell M, Crossley Ii DA. Impacts of Deepwater Horizon Crude Oil on Mahi-Mahi ( Coryphaena hippurus) Heart Cell Function. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:9895-9904. [PMID: 31343865 DOI: 10.1021/acs.est.9b03798] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Deepwater Horizon crude oil is comprised of polycyclic aromatic hydrocarbons that cause a number of cardiotoxic effects in marine fishes across all levels of biological organization and at different life stages. Although cardiotoxic impacts have been widely reported, the mechanisms underlying these impairments in adult fish remain understudied. In this study, we examined the impacts of crude oil on cardiomyocyte contractility and electrophysiological parameters in freshly isolated ventricular cardiomyocytes from adult mahi-mahi (Coryphaena hippurus). Cardiomyocytes directly exposed to oil exhibited reduced contractility over a range of environmentally relevant concentrations (2.8-12.9 μg l-1∑PAH). This reduction in contractility was most pronounced at higher stimulation frequencies, corresponding to the upper limits of previously measured in situ mahi heart rates. To better understand the mechanisms underlying impaired contractile function, electrophysiological studies were performed, which revealed oil exposure prolonged cardiomyocyte action potentials and disrupted potassium cycling (9.9-30.4 μg l-1∑PAH). This study is the first to measure cellular contractility in oil-exposed cardiomyocytes from a pelagic fish. Results from this study contribute to previously observed impairments to heart function and whole-animal exercise performance in mahi, underscoring the advantages of using an integrative approach in examining mechanisms of oil-induced cardiotoxicity in marine fish.
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Affiliation(s)
- Rachael M Heuer
- Department of Biological Sciences , University of North Texas , 1511 W. Sycamore Street , Denton Texas 76203 , United States
- Department of Marine Biology and Ecology , University of Miami Rosenstiel School of Marine and Atmospheric Science , 4600 Rickenbacker Causeway , Miami , Florida 33149 , United States
| | - Gina L J Galli
- University of Manchester, Faculty of Biology, Medicine and Health Sciences , The University of Manchester, Core Technology Facility , Grafton Street , Manchester M13 9PL , U.K
| | - Holly A Shiels
- University of Manchester, Faculty of Biology, Medicine and Health Sciences , The University of Manchester, Core Technology Facility , Grafton Street , Manchester M13 9PL , U.K
| | - Lynne A Fieber
- Department of Marine Biology and Ecology , University of Miami Rosenstiel School of Marine and Atmospheric Science , 4600 Rickenbacker Causeway , Miami , Florida 33149 , United States
| | - Georgina K Cox
- Department of Marine Biology and Ecology , University of Miami Rosenstiel School of Marine and Atmospheric Science , 4600 Rickenbacker Causeway , Miami , Florida 33149 , United States
- Department of Integrative Biology , University of Guelph , 50 Stone Road East , Guelph , Ontario Canada , N1G 2W1
| | - Edward M Mager
- Department of Biological Sciences , University of North Texas , 1511 W. Sycamore Street , Denton Texas 76203 , United States
- Department of Marine Biology and Ecology , University of Miami Rosenstiel School of Marine and Atmospheric Science , 4600 Rickenbacker Causeway , Miami , Florida 33149 , United States
| | - John D Stieglitz
- Department of Marine Ecosystems and Society , University of Miami Rosenstiel School of Marine and Atmospheric Science , 4600 Rickenbacker Causeway , Miami , Florida 33149 , United States
| | - Daniel D Benetti
- Department of Marine Ecosystems and Society , University of Miami Rosenstiel School of Marine and Atmospheric Science , 4600 Rickenbacker Causeway , Miami , Florida 33149 , United States
| | - Martin Grosell
- Department of Marine Biology and Ecology , University of Miami Rosenstiel School of Marine and Atmospheric Science , 4600 Rickenbacker Causeway , Miami , Florida 33149 , United States
| | - Dane A Crossley Ii
- Department of Biological Sciences , University of North Texas , 1511 W. Sycamore Street , Denton Texas 76203 , United States
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23
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Vagner M, Pante E, Viricel A, Lacoue-Labarthe T, Zambonino-Infante JL, Quazuguel P, Dubillot E, Huet V, Le Delliou H, Lefrançois C, Imbert-Auvray N. Ocean warming combined with lower omega-3 nutritional availability impairs the cardio-respiratory function of a marine fish. ACTA ACUST UNITED AC 2019; 222:jeb.187179. [PMID: 30630962 DOI: 10.1242/jeb.187179] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 12/20/2018] [Indexed: 12/27/2022]
Abstract
Highly unsaturated fatty acids of the omega-3 series (HUFA) are major constituents of cell membranes, yet are poorly synthesised de novo by consumers. Their production, mainly supported by aquatic microalgae, has been decreasing with global change. The consequences of such reductions may be profound for ectotherm consumers, as temperature tightly regulates the HUFA content in cell membranes, maintaining their functionality. Integrating individual, tissue and molecular approaches, we examined the consequences of the combined effects of temperature and HUFA depletion on the key cardio-respiratory functions of the golden grey mullet, an ectotherm grazer of high ecological importance. For 4 months, fish were exposed to two contrasting HUFA diets [4.8% eicosapentaenoic acid (EPA)+docosahexaenoic acid (DHA) on dry matter (DM) versus 0.2% EPA+DHA on DM] at 12 and 20°C. Ventricular force development coupled with gene expression profiles measured on cardiac muscle suggest that combining HUFA depletion with warmer temperatures leads to: (1) a proliferation of sarcolemmal and sarcoplasmic reticulum Ca2+ channels and (2) a higher force-generating ability by increasing extracellular Ca2+ influx via sarcolemmal channels when the heart has to sustain excessive effort due to stress and/or exercise. At the individual scale, these responses were associated with a greater aerobic scope, maximum metabolic rate and net cost of locomotion, suggesting the higher energy cost of this strategy. This impaired cardiac performance could have wider consequences for other physiological performance such as growth, reproduction or migration, all of which greatly depend on heart function.
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Affiliation(s)
- Marie Vagner
- UMR 7266 LIENSs (University of La Rochelle - CNRS), 2 rue Olympe de Gouges, 17000 La Rochelle, France
| | - Eric Pante
- UMR 7266 LIENSs (University of La Rochelle - CNRS), 2 rue Olympe de Gouges, 17000 La Rochelle, France
| | - Amelia Viricel
- UMR 7266 LIENSs (University of La Rochelle - CNRS), 2 rue Olympe de Gouges, 17000 La Rochelle, France
| | - Thomas Lacoue-Labarthe
- UMR 7266 LIENSs (University of La Rochelle - CNRS), 2 rue Olympe de Gouges, 17000 La Rochelle, France
| | | | - Patrick Quazuguel
- Ifremer, UMR 6539 LEMAR, Center Ifremer ZI Pointe du diable, 29280 Plouzané, France
| | - Emmanuel Dubillot
- UMR 7266 LIENSs (University of La Rochelle - CNRS), 2 rue Olympe de Gouges, 17000 La Rochelle, France
| | - Valerie Huet
- UMR 7266 LIENSs (University of La Rochelle - CNRS), 2 rue Olympe de Gouges, 17000 La Rochelle, France
| | - Herve Le Delliou
- Ifremer, UMR 6539 LEMAR, Center Ifremer ZI Pointe du diable, 29280 Plouzané, France
| | - Christel Lefrançois
- UMR 7266 LIENSs (University of La Rochelle - CNRS), 2 rue Olympe de Gouges, 17000 La Rochelle, France
| | - Nathalie Imbert-Auvray
- UMR 7266 LIENSs (University of La Rochelle - CNRS), 2 rue Olympe de Gouges, 17000 La Rochelle, France
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Is the teleost heart oxygen limited? - Insights using "hyperoxic" incubations of contracting cardiac tissue from rainbow trout. Comp Biochem Physiol A Mol Integr Physiol 2019; 231:124-130. [PMID: 30738911 DOI: 10.1016/j.cbpa.2019.01.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 01/24/2019] [Accepted: 01/29/2019] [Indexed: 11/22/2022]
Abstract
Considerable effort has been devoted to understanding the negative effects of reduced PO2 on cardiac function. Much less is known about the impacts of elevated PO2 (hyperoxia) on cardiac performance and energetics, especially in fishes. The fish heart is of particular interest because cardiac dependence on oxygen is extremely variable between species and the early evolution of fish occurred when atmospheric PO2 was higher than current conditions. Although extracellular PO2 is variable and normally does not exceed 21 kPa, recent evidence suggests that teleost cardiac function is stimulated at supraphysiological PO2 values. The purpose of this study was to address whether cardiac contractility and energy metabolism is responsive to elevated PO2 values in sexually-immature female rainbow trout. Isometric force development (contractility) and oxygen consumption (V̇O2) were recorded in electrically-paced ventricular preparations. Contractility and V̇O2decreased when superfusate PO2 was decreased from ~70 kPa to 57 kPa or 45 kPa. However, PO2 calculated at the preparation core was always above 18 kPa. This estimate, along with complete recovery of contractility and V̇O2 at ~70 kPa, suggests that decreases observed in cardiac performance were not due to tissue hypoxia at the lower PO2 levels. In conclusion, the heart of female rainbow trout may be oxygen-limited in vitro and this study raises new questions about the choice of appropriate PO2 for experimentation, the relevance of elevated and varying PO2 to measurements of cardiac performance, and the possible existence of an oxygen sensor within rainbow trout cardiomyocytes.
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Joyce W, Williams CJA, Iversen S, Henriksen PG, Bayley M, Wang T. The effects of endogenous and exogenous catecholamines on hypoxic cardiac performance in red-bellied piranhas. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2018; 331:27-37. [DOI: 10.1002/jez.2233] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 08/01/2018] [Accepted: 08/24/2018] [Indexed: 11/06/2022]
Affiliation(s)
- William Joyce
- Department of Zoophysiology; Aarhus University; Aarhus Denmark
| | | | - Sofie Iversen
- Department of Zoophysiology; Aarhus University; Aarhus Denmark
| | | | - Mark Bayley
- Department of Zoophysiology; Aarhus University; Aarhus Denmark
| | - Tobias Wang
- Department of Zoophysiology; Aarhus University; Aarhus Denmark
- Aarhus Institute of Advanced Studies; Aarhus University; Aarhus Denmark
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Roberts JC, Syme DA. Effects of epinephrine exposure on contractile performance of compact and spongy myocardium from rainbow trout (Oncorhynchus mykiss) during hypoxia. FISH PHYSIOLOGY AND BIOCHEMISTRY 2018; 44:49-62. [PMID: 28795283 DOI: 10.1007/s10695-017-0412-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 07/21/2017] [Indexed: 06/07/2023]
Abstract
Hypoxia results in elevated circulating epinephrine for many fish species, and this is likely important for maintaining cardiac function. The aims of this study were to assess how hypoxia impacts contractile responses of ventricular compact and spongy myocardium from rainbow trout (Oncorhynchus mykiss) and to assess how and if epinephrine may protect myocardial performance from a depressive effect of hypoxia. Work output and maximum contraction rate of isolated preparations of spongy and compact ventricular myocardium from rainbow trout were measured. Tissues were exposed to the blood PO2 that they experience in vivo during environmental normoxia and hypoxia and also to low (5 nM) and high (500 nM) levels of epinephrine in 100% air saturation (PO2 20.2 kPa) and during hypoxia (PO2 2 kPa, 10% air saturation). It was hypothesized that hypoxia would result in a decrease in work output and maximum contraction rate in both tissue types, but that epinephrine exposure would mitigate the effect. Hypoxia resulted in a decline in net work output of both tissue types, but a decline in maximum contraction rate of only compact myocardium. Epinephrine restored the maximum contraction rate of compact myocardium in hypoxia, appeared to slightly enhance work output of only compact myocardium in air saturation but surprisingly not during hypoxia, and restored net work of hypoxic spongy myocardium toward normoxic levels. These results indicate hypoxia has a similar depressive effect on both layers of ventricular myocardium, but that high epinephrine may be important for maintaining inotropy in spongy myocardium and chronotropy in compact myocardium during hypoxia.
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Affiliation(s)
- Jordan C Roberts
- Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N1N4, Canada
| | - Douglas A Syme
- Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N1N4, Canada.
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Monteiro DA, Taylor EW, Rantin FT, Kalinin AL. Impact of waterborne and trophic mercury exposures on cardiac function of two ecologically distinct Neotropical freshwater fish Brycon amazonicus and Hoplias malabaricus. Comp Biochem Physiol C Toxicol Pharmacol 2017; 201:26-34. [PMID: 28939505 DOI: 10.1016/j.cbpc.2017.09.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 09/14/2017] [Accepted: 09/16/2017] [Indexed: 01/09/2023]
Abstract
Metal pollutants have been considered one of the main factors underlying the depletion of biodiversity in natural populations unbalancing aquatic environments. The aim of this study was to evaluate the effects of exposure to inorganic Hg on myocardial contractility and the electrocardiogram (ECG) of two ecologically distinct Neotropical fish species, namely: matrinxã (Brycon amazonicus) and trahira (Hoplias malabaricus). Matrinxãs were exposed to a sublethal concentration of 0.1mgL-1 of Hg in water for 96h. Trahiras were exposed to dietary Hg doses (0.45mg of Hg, each 4days, for 30days) using juvenile B. amazonicus as the prey vehicle. Hg exposures decreased myocardial isometric twitch force development, harmed contraction/relaxation dynamics and cardiac pumping capacity (CPC), and reduced the relative contribution of the calcium stored in the sarcoplasmic reticulum (SR) to excitation contraction (EC) coupling in both fish species. Analysis of the ECG revealed that Hg impaired electrical conduction across the heart, inducing first degree atrioventricular block and lengthening the plateau phase of action potential duration. In trahira trophic doses of Hg induced a marked bradycardia, increasing the duration of the ventricular action potential and delaying atrial and ventricular depolarization. These findings indicate that both acute and long-term Hg exposure, by different routes is cardiotoxic to matrinxã and trahira. Hg potently impaired intracellular calcium kinetics in the cardiomyocytes, myocardium contractility, and electrical conduction across the heart, all of which can be implicated in decreased cardiac output and putative heart failure.
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Affiliation(s)
- Diana A Monteiro
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos 13565-905, São Paulo, Brazil.
| | - Edwin W Taylor
- School of Biological Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Francisco T Rantin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos 13565-905, São Paulo, Brazil
| | - Ana L Kalinin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos 13565-905, São Paulo, Brazil
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Jensen DL, Overgaard J, Wang T, Gesser H, Malte H. Temperature effects on aerobic scope and cardiac performance of European perch (Perca fluviatilis). J Therm Biol 2017; 68:162-169. [PMID: 28797476 DOI: 10.1016/j.jtherbio.2017.04.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 04/14/2017] [Accepted: 04/18/2017] [Indexed: 10/19/2022]
Abstract
Several recent studies have highlighted how impaired cardiac performance at high temperatures and in hypoxia may compromise the capacity for oxygen transport. Thus, at high temperatures impaired cardiac capacity is proposed to reduce oxygen transport to a degree that lowers aerobic scope and compromises thermal tolerance (the oxygen- and capacity-limited thermal tolerance (OCLTT) hypothesis). To investigate this hypothesis, we measured aerobic and cardiac performance of a eurythermal freshwater teleost, the European perch (Perca fluviatilis). Rates of oxygen consumption were measured during rest and activity at temperatures between 5°C and 27°C, and we evaluated cardiac function by in vivo measurements of heart rate and in vitro studies to determine contractility of myocardial strips. Aerobic scope increased progressively from 5°C to 21°C, after which it levelled off. Heart rate showed a similar response. We found little difference between resting and active heart rate at high temperature suggesting that increased cardiac scope during activity is primarily related to changes in stroke volume. To examine the effects of temperature on cardiac capacity, we measured isometric force development in electrically paced myocardial preparations during different combinations of temperature, pacing frequency, oxygenation and adrenergic stimulation. The force-frequency product increased markedly upon adrenergic stimulation at 21 and 27°C (with higher effects at 21°C) and the cardiac preparations were highly sensitive to hypoxia. These findings suggest that at (critically) high temperatures, cardiac output may diminish due to a decreased effect of adrenergic stimulation and that this effect may be further exacerbated if the heart becomes hypoxic. Hence cardiac limitations may contribute to the inability to increase aerobic scope at high temperatures in the European perch (Perca fluviatilis).
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Affiliation(s)
| | - Johannes Overgaard
- Department of Bioscience, Zoophysiology, Aarhus University, Aarhus, Denmark
| | - Tobias Wang
- Department of Bioscience, Zoophysiology, Aarhus University, Aarhus, Denmark
| | - Hans Gesser
- Department of Bioscience, Zoophysiology, Aarhus University, Aarhus, Denmark
| | - Hans Malte
- Department of Bioscience, Zoophysiology, Aarhus University, Aarhus, Denmark.
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Crossley DA, Burggren WW, Reiber CL, Altimiras J, Rodnick KJ. Mass Transport: Circulatory System with Emphasis on Nonendothermic Species. Compr Physiol 2016; 7:17-66. [PMID: 28134997 DOI: 10.1002/cphy.c150010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Mass transport can be generally defined as movement of material matter. The circulatory system then is a biological example given its role in the movement in transporting gases, nutrients, wastes, and chemical signals. Comparative physiology has a long history of providing new insights and advancing our understanding of circulatory mass transport across a wide array of circulatory systems. Here we focus on circulatory function of nonmodel species. Invertebrates possess diverse convection systems; that at the most complex generate pressures and perform at a level comparable to vertebrates. Many invertebrates actively modulate cardiovascular function using neuronal, neurohormonal, and skeletal muscle activity. In vertebrates, our understanding of cardiac morphology, cardiomyocyte function, and contractile protein regulation by Ca2+ highlights a high degree of conservation, but differences between species exist and are coupled to variable environments and body temperatures. Key regulators of vertebrate cardiac function and systemic blood pressure include the autonomic nervous system, hormones, and ventricular filling. Further chemical factors regulating cardiovascular function include adenosine, natriuretic peptides, arginine vasotocin, endothelin 1, bradykinin, histamine, nitric oxide, and hydrogen sulfide, to name but a few. Diverse vascular morphologies and the regulation of blood flow in the coronary and cerebral circulations are also apparent in nonmammalian species. Dynamic adjustments of cardiovascular function are associated with exercise on land, flying at high altitude, prolonged dives by marine mammals, and unique morphology, such as the giraffe. Future studies should address limits of gas exchange and convective transport, the evolution of high arterial pressure across diverse taxa, and the importance of the cardiovascular system adaptations to extreme environments. © 2017 American Physiological Society. Compr Physiol 7:17-66, 2017.
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Affiliation(s)
- Dane A Crossley
- Department of Biological Sciences, University of North Texas, Denton, Texas, USA
| | - Warren W Burggren
- Department of Biological Sciences, University of North Texas, Denton, Texas, USA
| | - Carl L Reiber
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, USA
| | - Jordi Altimiras
- AVIAN Behavioral Genomics and Physiology, IFM Biology, Linköping University, Linköping, Sweden
| | - Kenneth J Rodnick
- Department of Biological Sciences, Idaho State University, Pocatello, Idaho, USA
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Larsen J, Bushnell P, Steffensen J, Pedersen M, Qvortrup K, Brill R. Characterization of the functional and anatomical differences in the atrial and ventricular myocardium from three species of elasmobranch fishes: smooth dogfish (Mustelus canis), sandbar shark (Carcharhinus plumbeus), and clearnose skate (Raja eglanteria). J Comp Physiol B 2016; 187:291-313. [PMID: 27686667 DOI: 10.1007/s00360-016-1034-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 08/25/2016] [Accepted: 09/13/2016] [Indexed: 01/15/2023]
Abstract
We assessed the functional properties in atrial and ventricular myocardium (using isolated cardiac strips) of smooth dogfish (Mustelus canis), clearnose skate (Raja eglanteria), and sandbar shark (Carcharhinus plumbeus) by blocking Ca2+ release from the sarcoplasmic reticulum (SR) with ryanodine and thapsigargin and measuring the resultant changes in contraction-relaxation parameters and the force-frequency relationship at 20 °C and 30 °C. We also examined ultrastructural differences with electron microscopy. In tissues from smooth dogfish, net force (per cross-sectional area) and measures of the speeds of contraction and relaxation were all higher in atrial than ventricular myocardium at both temperatures. Atrial-ventricular differences were evident in the other two species primarily in measures of the rates of contraction and relaxation. Ryanodine-thapsigargin treatment reduced net force and its maximum positive first derivative (i.e., contractility), and increased time to 50 % relaxation in atrial tissue from smooth dogfish at 30 °C. It also increased times to peak force and half relaxation in clearnose skate atrial and ventricular tissue at both temperatures, but only in atrial tissue from sandbar shark at 30 °C; indicating that SR involvement in excitation-contraction (EC) coupling is species- and temperature-specific in elasmobranch fishes, as it is in teleost fishes. Atrial and ventricular myocardium from all three species displayed a negative force-frequency relationship, but there was no evidence that SR involvement in EC coupling was influenced by heart rate. SR was evident in electron micrographs, generally located in proximity to mitochondria and intercalated discs, and to a lesser extent between the myofibrils; with mitochondria being more numerous in ventricular than atrial myocardium in all three species.
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Affiliation(s)
- Julie Larsen
- Marine Biological Section, University of Copenhagen, Strandpromenaden 5, 3000, Helsingør, Denmark
| | - Peter Bushnell
- Department of Biology, Indiana University South Bend, 1700 Mishawaka Avenue, South Bend, IN, 46634-7111, USA
| | - John Steffensen
- Marine Biological Section, University of Copenhagen, Strandpromenaden 5, 3000, Helsingør, Denmark
| | - Morten Pedersen
- Department of Science and Environment, Roskilde University, Universitetsvej 1, 4000, Roskilde, Denmark
| | - Klaus Qvortrup
- Department of Biomedical Sciences/CFIM, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Richard Brill
- Behavioral Ecology Branch, Ecosystems Processes Division, Northeast Fisheries Science Center, National Marine Fisheries Service, NOAA, Sandy Hook, NJ, USA. .,Virginia Institute of Marine Science, PO Box 1346, Gloucester Point, VA, 23062, USA.
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Ekström A, Brijs J, Clark TD, Gräns A, Jutfelt F, Sandblom E. Cardiac oxygen limitation during an acute thermal challenge in the European perch: effects of chronic environmental warming and experimental hyperoxia. Am J Physiol Regul Integr Comp Physiol 2016; 311:R440-9. [PMID: 27280433 DOI: 10.1152/ajpregu.00530.2015] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 06/07/2016] [Indexed: 11/22/2022]
Abstract
Oxygen supply to the heart has been hypothesized to limit cardiac performance and whole animal acute thermal tolerance (CTmax) in fish. We tested these hypotheses by continuously measuring venous oxygen tension (Pvo2) and cardiovascular variables in vivo during acute warming in European perch (Perca fluviatilis) from a reference area during summer (18°C) and a chronically heated area (Biotest enclosure) that receives warm effluent water from a nuclear power plant and is normally 5-10°C above ambient (24°C at the time of experiments). While CTmax was 2.2°C higher in Biotest compared with reference perch, the peaks in cardiac output and heart rate prior to CTmax occurred at statistically similar Pvo2 values (2.3-4.0 kPa), suggesting that cardiac failure occurred at a common critical Pvo2 threshold. Environmental hyperoxia (200% air saturation) increased Pvo2 across temperatures in reference fish, but heart rate still declined at a similar temperature. CTmax of reference fish increased slightly (by 0.9°C) in hyperoxia, but remained significantly lower than in Biotest fish despite an improved cardiac output due to an elevated stroke volume. Thus, while cardiac oxygen supply appears critical to elevate stroke volume at high temperatures, oxygen limitation may not explain the bradycardia and arrhythmia that occur prior to CTmax Acute thermal tolerance and its thermal plasticity can, therefore, only be partially attributed to cardiac failure from myocardial oxygen limitations, and likely involves limiting factors on multiple organizational levels.
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Affiliation(s)
- Andreas Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden;
| | - Jeroen Brijs
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Timothy D Clark
- Australian Institute of Marine Science, Townsville, Queensland, Australia; and
| | - Albin Gräns
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Skara, Sweden
| | - Fredrik Jutfelt
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
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Lee L, Genge CE, Cua M, Sheng X, Rayani K, Beg MF, Sarunic MV, Tibbits GF. Functional Assessment of Cardiac Responses of Adult Zebrafish (Danio rerio) to Acute and Chronic Temperature Change Using High-Resolution Echocardiography. PLoS One 2016; 11:e0145163. [PMID: 26730947 PMCID: PMC4701665 DOI: 10.1371/journal.pone.0145163] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 11/27/2015] [Indexed: 12/21/2022] Open
Abstract
The zebrafish (Danio rerio) is an important organism as a model for understanding vertebrate cardiovascular development. However, little is known about adult ZF cardiac function and how contractile function changes to cope with fluctuations in ambient temperature. The goals of this study were to: 1) determine if high resolution echocardiography (HRE) in the presence of reduced cardiodepressant anesthetics could be used to accurately investigate the structural and functional properties of the ZF heart and 2) if the effect of ambient temperature changes both acutely and chronically could be determined non-invasively using HRE in vivo. Heart rate (HR) appears to be the critical factor in modifying cardiac output (CO) with ambient temperature fluctuation as it increases from 78 ± 5.9 bpm at 18°C to 162 ± 9.7 bpm at 28°C regardless of acclimation state (cold acclimated CA- 18°C; warm acclimated WA- 28°C). Stroke volume (SV) is highest when the ambient temperature matches the acclimation temperature, though this difference did not constitute a significant effect (CA 1.17 ± 0.15 μL at 18°C vs 1.06 ± 0.14 μl at 28°C; WA 1.10 ± 0.13 μL at 18°C vs 1.12 ± 0.12 μl at 28°C). The isovolumetric contraction time (IVCT) was significantly shorter in CA fish at 18°C. The CA group showed improved systolic function at 18°C in comparison to the WA group with significant increases in both ejection fraction and fractional shortening and decreases in IVCT. The decreased early peak (E) velocity and early peak velocity / atrial peak velocity (E/A) ratio in the CA group are likely associated with increased reliance on atrial contraction for ventricular filling.
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Affiliation(s)
- Ling Lee
- Molecular Cardiac Physiology Group, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
- Child and Family Research Institute, Department of Cardiovascular Science, 950 West 28th Ave, Vancouver, BC V5Z 4H4, Canada
| | - Christine E. Genge
- Child and Family Research Institute, Department of Cardiovascular Science, 950 West 28th Ave, Vancouver, BC V5Z 4H4, Canada
| | - Michelle Cua
- School of Engineering Science, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Xiaoye Sheng
- Molecular Cardiac Physiology Group, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
- Child and Family Research Institute, Department of Cardiovascular Science, 950 West 28th Ave, Vancouver, BC V5Z 4H4, Canada
| | - Kaveh Rayani
- Molecular Cardiac Physiology Group, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Mirza F. Beg
- School of Engineering Science, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Marinko V. Sarunic
- School of Engineering Science, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Glen F. Tibbits
- Molecular Cardiac Physiology Group, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
- Child and Family Research Institute, Department of Cardiovascular Science, 950 West 28th Ave, Vancouver, BC V5Z 4H4, Canada
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Joyce W, Axelsson M, Wang T. Autoregulation of cardiac output is overcome by adrenergic stimulation in the anaconda heart. J Exp Biol 2016; 220:336-340. [DOI: 10.1242/jeb.149237] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 11/03/2016] [Indexed: 11/20/2022]
Abstract
Most vertebrates increase cardiac output during activity by elevating heart rate with relatively stable stroke volume. However, several studies have demonstrated ‘intrinsic autoregulation’ of cardiac output where artificially increased heart rate is associated with decreased stroke volume, leaving cardiac output unchanged. We explored the capacity of noradrenaline to overcome autoregulation in the anaconda heart. Electrically pacing in situ perfused hearts from the intrinsic heart rate to the maximum attainable resulted in a proportional decrease in stroke volume. However, noradrenaline, which increased heart rate to the same frequency as pacing, maintained stroke volume and thus increased cardiac output. In atrial and ventricular preparations noradrenaline significantly increased the force of contraction and contraction kinetics. Thus, the increased contractility associated with adrenergic stimulation ameliorates filling limitations at high heart rates. Although heart rate appears the primary regulated variable during activity, this may only be achieved with compensatory amendments in myocardial contractility provided by adrenergic stimulation.
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Affiliation(s)
- William Joyce
- Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
| | - Michael Axelsson
- Department of Biological and Environmental Sciences, University of Gothenburg, 405 30 Gothenburg, Sweden
| | - Tobias Wang
- Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
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Tikkanen E, Haverinen J, Egginton S, Hassinen M, Vornanen M. Effects of prolonged anoxia on electrical activity of the heart in Crucian carp (Carassius carassius). J Exp Biol 2016; 220:445-454. [DOI: 10.1242/jeb.145177] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 11/15/2016] [Indexed: 01/08/2023]
Abstract
The effects of sustained anoxia on cardiac electrical excitability were examined in the anoxia-tolerant Crucian carp (Carassius carassius). The electrocardiogram (ECG) and expression of excitation-contraction coupling genes were studied in fish acclimatised to normoxia in summer (+18°C) or winter (+2°C), and in winter fish after 1, 3 and 6 weeks of anoxia. Anoxia induced a sustained bradycardia from a heart rate of 10.3±0.77 to 4.1±0.29 bpm (P<0.05) after 5 weeks, and heart rate slowly recovered to control levels when oxygen was restored. Heart rate variability greatly increased under anoxia, and completely recovered under re-oxygenation. The RT interval increased from 2.8±0.34 s in normoxia to 5.8±0.44 s under anoxia (P<0.05), which reflects a doubling of the ventricular action potential (AP) duration. Acclimatisation to winter induced extensive changes in gene expression relative to summer-acclimatised fish, including depression in those coding for the sarcoplasmic reticulum calcium pump (Serca2-q2) and ATP-sensitive K+ channels (Kir6.2) (P<0.05). Genes of delayed rectifier K+ (kcnh6) and Ca2+ channels (cacna1c) were up-regulated in winter fish (P<0.05). In contrast, the additional challenge of anoxia caused only minor changes in gene expression, e.g. depressed expression of Kir2.2b K+ channel gene (kcnj12b), whereas expression of Ca2+ (cacna1a, -c and –g) and Na+ channel genes (scn4a and scn5a) were not affected. These data suggest that low temperature pre-conditions the Crucian carp heart for winter anoxia, whereas sustained anoxic bradycardia and prolongation of AP duration are directly induced by oxygen shortage without major changes in gene expression.
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Affiliation(s)
- Elisa Tikkanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
| | - Jaakko Haverinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
| | | | - Minna Hassinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
| | - Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
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Monteiro DA, Kalinin AL, Selistre-de-Araujo HS, Vasconcelos ES, Rantin FT. Alternagin-C (ALT-C), a disintegrin-like protein from Rhinocerophis alternatus snake venom promotes positive inotropism and chronotropism in fish heart. Toxicon 2015; 110:1-11. [PMID: 26615089 DOI: 10.1016/j.toxicon.2015.11.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 11/09/2015] [Accepted: 11/18/2015] [Indexed: 11/29/2022]
Abstract
Alternagin-C (ALT-C) is a disintegrin-like protein purified from the venom of the snake, Rhinocerophis alternatus. Recent studies showed that ALT-C is able to induce vascular endothelial growth factor (VEGF) expression, endothelial cell proliferation and migration, angiogenesis and to increase myoblast viability. This peptide, therefore, can play a crucial role in tissue regeneration mechanisms. The aim of this study was to evaluate the effects of a single dose of alternagin-C (0.5 mg kg(-1), via intra-arterial) on in vitro cardiac function of the freshwater fish traíra, Hoplias malabaricus, after 7 days. ALT-C treatment increased the cardiac performance promoting: 1) significant increases in the contraction force and in the rates of contraction and relaxation with concomitant decreases in the values of time to the peak tension and time to half- and 90% relaxation; 2) improvement in the cardiac pumping capacity and maximal electrical stimulation frequency, shifting the optimum frequency curve upward and to the right; 3) increases in myocardial VEGF levels and expression of key Ca(2+)-cycling proteins such as SERCA (sarcoplasmic reticulum Ca(2+)-ATPase), PLB (phospholamban), and NCX (Na(+)/Ca(2+) exchanger); 4) abolishment of the typical negative force-frequency relationship of fish myocardium. In conclusion, this study indicates that ALT-C improves cardiac function, by increasing Ca(2+) handling efficiency leading to a positive inotropism and chronotropism. The results suggest that ALT-C may lead to better cardiac output regulation indicating its potential application in therapies for cardiac contractile dysfunction.
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Affiliation(s)
- D A Monteiro
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil.
| | - A L Kalinin
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
| | - H S Selistre-de-Araujo
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
| | - E S Vasconcelos
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
| | - F T Rantin
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
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Seasonal acclimatization of the cardiac potassium currents (IK1 and IKr) in an arctic marine teleost, the navaga cod (Eleginus navaga). J Comp Physiol B 2015; 185:883-90. [PMID: 26253844 DOI: 10.1007/s00360-015-0925-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 07/13/2015] [Accepted: 07/28/2015] [Indexed: 10/23/2022]
Abstract
Several freshwater fishes of north-temperate latitudes exhibit marked seasonal changes in cardiac action potential (AP) waveform as an outcome of temperature-dependent changes in the density of delayed rectifiers (IKr, IKs) and inward rectifier (IK1) potassium currents. Thus far, ionic mechanisms of cardiac excitability in arctic marine fishes have not been examined. To this end we examined ventricular AP and the role of two major potassium currents (IK1, IKr) in repolarization of cardiac AP in winter-acclimatized (WA, caught in March) and summer-acclimatized (SA, caught in September) navaga cod (Eleginus navaga) of the White Sea. The duration of ventricular AP of WA navaga at 3 °C (APD50 = 659.5 ± 32.8 ms) was similar to the AP duration of SA navaga at 12 °C (APD50 = 543.9 ± 14.6 ms) (p > 0.05) indicating complete thermal compensation of AP duration. This acclimation effect was associated with strong up-regulation of the cardiac potassium currents in winter. Densities of ventricular IK1 (at -120 mV) and IKr (at +50 mV) of the WA navaga at 3 °C were 2.9 times and 2.8 times, respectively, higher than those of the SA navaga at 12 °C, thus indicating marked thermal overcompensation. Qualitatively similar results were obtained from atrial myocytes. Seasonal changes in IK1 and IKr are more than sufficient to explain the complete thermal compensation of ventricular AP duration. The excellent acclimation capacity of cardiac excitability of the navaga cod is probably needed to maintain high cardiac performance at subzero temperatures in winter and to increase thermal resilience of cardiac function under seasonally variable arctic temperature conditions.
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Haustein M, Hannes T, Trieschmann J, Verhaegh R, Köster A, Hescheler J, Brockmeier K, Adelmann R, Khalil M. Excitation-contraction coupling in zebrafish ventricular myocardium is regulated by trans-sarcolemmal Ca2+ influx and sarcoplasmic reticulum Ca2+ release. PLoS One 2015; 10:e0125654. [PMID: 25938412 PMCID: PMC4418605 DOI: 10.1371/journal.pone.0125654] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 03/17/2015] [Indexed: 01/19/2023] Open
Abstract
Zebrafish (Danio rerio) have become a popular model in cardiovascular research mainly due to identification of a large number of mutants with structural defects. In recent years, cardiomyopathies and other diseases influencing contractility of the heart have been studied in zebrafish mutants. However, little is known about the regulation of contractility of the zebrafish heart on a tissue level. The aim of the present study was to elucidate the role of trans-sarcolemmal Ca2+-flux and sarcoplasmic reticulum Ca2+-release in zebrafish myocardium. Using isometric force measurements of fresh heart slices, we characterised the effects of changes of the extracellular Ca2+-concentration, trans-sarcolemmal Ca2+-flux via L-type Ca2+-channels and Na+-Ca2+-exchanger, and Ca2+-release from the sarcoplasmic reticulum as well as beating frequency and β-adrenergic stimulation on contractility of adult zebrafish myocardium. We found an overall negative force-frequency relationship (FFR). Inhibition of L-type Ca2+-channels by verapamil (1 μM) decreased force of contraction to 22±7% compared to baseline (n=4, p<0.05). Ni2+ was the only substance to prolong relaxation (5 mM, time after peak to 50% relaxation: 73±3 ms vs. 101±8 ms, n=5, p<0.05). Surprisingly though, inhibition of the sarcoplasmic Ca2+-release decreased force development to 54±3% in ventricular (n=13, p<0.05) and to 52±8% in atrial myocardium (n=5, p<0.05) suggesting a substantial role of SR Ca2+-release in force generation. In line with this finding, we observed significant post pause potentiation after pauses of 5 s (169±7% force compared to baseline, n=8, p<0.05) and 10 s (198±9% force compared to baseline, n=5, p<0.05) and mildly positive lusitropy after β-adrenergic stimulation. In conclusion, force development in adult zebrafish ventricular myocardium requires not only trans-sarcolemmal Ca2+-flux, but also intact sarcoplasmic reticulum Ca2+-cycling. In contrast to mammals, FFR is strongly negative in the zebrafish heart. These aspects need to be considered when using zebrafish to model human diseases of myocardial contractility.
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Affiliation(s)
- Moritz Haustein
- Department of Paediatric Cardiology, Cologne Heart Centre, Medical Faculty, University of Cologne, Cologne, North Rhine-Westphalia, Germany
| | - Tobias Hannes
- Department of Paediatric Cardiology, Cologne Heart Centre, Medical Faculty, University of Cologne, Cologne, North Rhine-Westphalia, Germany
- Institute for Neurophysiology, Medical Faculty, University of Cologne, Cologne, North Rhine-Westphalia, Germany
- * E-mail:
| | - Jan Trieschmann
- Institute for Neurophysiology, Medical Faculty, University of Cologne, Cologne, North Rhine-Westphalia, Germany
| | - Rabea Verhaegh
- Institute of Physiological Chemistry, University Hospital Essen, Essen, North Rhine-Westphalia, Germany
| | - Annette Köster
- Institute for Neurophysiology, Medical Faculty, University of Cologne, Cologne, North Rhine-Westphalia, Germany
| | - Jürgen Hescheler
- Institute for Neurophysiology, Medical Faculty, University of Cologne, Cologne, North Rhine-Westphalia, Germany
| | - Konrad Brockmeier
- Department of Paediatric Cardiology, Cologne Heart Centre, Medical Faculty, University of Cologne, Cologne, North Rhine-Westphalia, Germany
| | - Roland Adelmann
- Department of Paediatric Cardiology, Cologne Heart Centre, Medical Faculty, University of Cologne, Cologne, North Rhine-Westphalia, Germany
| | - Markus Khalil
- Department of Paediatric Cardiology, University Hospital of Giessen and Marburg, University of Giessen and Marburg, Giessen, Hessen, Germany
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Joyce W, Simonsen M, Gesser H, Wang T. The effects of hypoxic bradycardia and extracellular HCO3−/CO2 on hypoxic performance in the eel heart. J Exp Biol 2015; 219:302-5. [DOI: 10.1242/jeb.130971] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 11/16/2015] [Indexed: 10/22/2022]
Abstract
During hypoxia fishes exhibit a characteristic ‘hypoxic bradycardia’, the functional significance of which remains debated. Here, we investigated the hypothesis that hypoxic bradycardia primarily safeguards cardiac performance. In preparations from the European eel (Anguilla anguilla), a decrease in stimulation frequency from 40 to 15 beats per minute, which replicates hypoxic bradycardia in vivo, vastly improved cardiac performance during hypoxia in vitro. As eels display dramatic shifts in extracellular HCO3−/CO2, we further investigated the effect this has upon hypoxic cardiac performance. Elevations from 10 mM HCO3−/ 1% to 40 mM HCO3−/ 4% CO2 had few effects on performance, however further, but still physiologically relevant, increases to 70 mM HCO3−/ 7% CO2 compromised hypoxia tolerance. We revealed a four-way interaction between HCO3−/CO2, contraction frequency, hypoxia and performance over time, whereby the benefit of hypoxic bradycardia was most prolonged at 10 mM HCO3−/ 1% CO2. Together, our data suggest that hypoxic bradycardia greatly benefits cardiac performance, but its significance may be context-specific.
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Affiliation(s)
- William Joyce
- Zoophysiology, Department of Bioscience, Aarhus University, Building 1131, Universitetsparken, 8000 Aarhus C, Denmark
| | - Maj Simonsen
- Zoophysiology, Department of Bioscience, Aarhus University, Building 1131, Universitetsparken, 8000 Aarhus C, Denmark
| | - Hans Gesser
- Zoophysiology, Department of Bioscience, Aarhus University, Building 1131, Universitetsparken, 8000 Aarhus C, Denmark
| | - Tobias Wang
- Zoophysiology, Department of Bioscience, Aarhus University, Building 1131, Universitetsparken, 8000 Aarhus C, Denmark
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41
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Elasmobranch Cardiovascular System. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/b978-0-12-801286-4.00001-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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42
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Battiprolu PK, Rodnick KJ. Dichloroacetate selectively improves cardiac function and metabolism in female and male rainbow trout. Am J Physiol Heart Circ Physiol 2014; 307:H1401-11. [PMID: 25217653 PMCID: PMC4233302 DOI: 10.1152/ajpheart.00755.2013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 09/11/2014] [Indexed: 01/08/2023]
Abstract
Cardiac tissue from female rainbow trout demonstrates a sex-specific preference for exogenous glucose and glycolysis, impaired Ca(2+) handling, and a greater tolerance for hypoxia and reoxygenation than cardiac tissue from male rainbow trout. We tested the hypothesis that dichloroacetate (DCA), an activator of pyruvate dehydrogenase, enhances cardiac energy metabolism and Ca(2+) handling in female preparations and provide cardioprotection for hypoxic male tissue. Ventricle strips from sexually immature fish with very low (male) and nondetectable (female) plasma sex steroids were electrically paced in oxygenated or hypoxic Ringer solution with or without 1 mM DCA. In the presence of 5 mM glucose, aerobic tissue from male trout could be paced at a higher frequency (1.79 vs. 1.36 Hz) with lower resting tension and less contractile dysfunction than female tissue. At 0.5 Hz, DCA selectively reduced resting tension below baseline values and lactate efflux by 75% in aerobic female ventricle strips. DCA improved the functional recovery of developed twitch force, reduced lactate efflux by 50%, and doubled citrate in male preparations after hypoxia-reoxygenation. Independent of female sex steroids, reduced myocardial pyruvate dehydrogenase activity and impaired carbohydrate oxidation might explain the higher lactate efflux, compromised function of the sarcoplasmic reticulum, and reduced mechanical performance of aerobic female tissue. Elevated oxidative metabolism and reduced glycolysis might also underlie the beneficial effects of DCA on the mechanical recovery of male cardiac tissue after hypoxia-reoxygenation. These results support the use of rainbow trout as an experimental model of sex differences of cardiovascular energetics and function, with the potential for modifying metabolic phenotypes and cardioprotection independent of sex steroids.
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Affiliation(s)
- Pavan K Battiprolu
- Department of Biological Sciences, Idaho State University, Pocatello, Idaho
| | - Kenneth J Rodnick
- Department of Biological Sciences, Idaho State University, Pocatello, Idaho
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43
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Cros C, Sallé L, Warren DE, Shiels HA, Brette F. The calcium stored in the sarcoplasmic reticulum acts as a safety mechanism in rainbow trout heart. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1493-501. [PMID: 25377479 PMCID: PMC4269670 DOI: 10.1152/ajpregu.00127.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Cardiomyocyte contraction depends on rapid changes in intracellular Ca2+. In mammals, Ca2+ influx as L-type Ca2+ current (ICa) triggers the release of Ca2+ from sarcoplasmic reticulum (SR) and Ca2+-induced Ca2+ release (CICR) is critical for excitation-contraction coupling. In fish, the relative contribution of external and internal Ca2+ is unclear. Here, we characterized the role of ICa to trigger SR Ca2+ release in rainbow trout ventricular myocytes using ICa regulation by Ca2+ as an index of CICR. ICa was recorded with a slow (EGTA) or fast (BAPTA) Ca2+ chelator in control and isoproterenol conditions. In the absence of β-adrenergic stimulation, the rate of ICa inactivation was not significantly different in EGTA and BAPTA (27.1 ± 1.8 vs. 30.3 ± 2.4 ms), whereas with isoproterenol (1 μM), inactivation was significantly faster with EGTA (11.6 ± 1.7 vs. 27.3 ± 1.6 ms). When barium was the charge carrier, inactivation was significantly slower in both conditions (61.9 ± 6.1 vs. 68.0 ± 8.7 ms, control, isoproterenol). Quantification revealed that without isoproterenol, only 39% of ICa inactivation was due to Ca2+, while with isoproterenol, inactivation was Ca2+-dependent (∼65%) and highly reliant on SR Ca2+ (∼46%). Thus, SR Ca2+ is not released in basal conditions, and ICa is the main trigger of contraction, whereas during a stress response, SR Ca2+ is an important source of cytosolic Ca2+. This was not attributed to differences in SR Ca2+ load because caffeine-induced transients were not different in both conditions. Therefore, Ca2+ stored in SR of trout cardiomyocytes may act as a safety mechanism, allowing greater contraction when higher contractility is required, such as stress or exercise.
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Affiliation(s)
- Caroline Cros
- Faculty of Life Sciences, The University of Manchester, Core Technology Facility, Manchester, United Kingdom; and
| | | | - Daniel E Warren
- Faculty of Life Sciences, The University of Manchester, Core Technology Facility, Manchester, United Kingdom; and
| | - Holly A Shiels
- Faculty of Life Sciences, The University of Manchester, Core Technology Facility, Manchester, United Kingdom; and
| | - Fabien Brette
- Faculty of Life Sciences, The University of Manchester, Core Technology Facility, Manchester, United Kingdom; and
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44
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Ekström A, Jutfelt F, Sandblom E. Effects of autonomic blockade on acute thermal tolerance and cardioventilatory performance in rainbow trout, Oncorhynchus mykiss. J Therm Biol 2014; 44:47-54. [PMID: 25086973 DOI: 10.1016/j.jtherbio.2014.06.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 05/30/2014] [Accepted: 06/02/2014] [Indexed: 10/25/2022]
Abstract
Predicted future increases in global temperature may impose challenges for ectothermic animals like fish, but the physiological mechanisms determining the critical thermal maximum (CTmax) are not well understood. One hypothesis suggests that impaired cardiac performance, limited by oxygen supply, is an important underlying mechanism. Since vagal bradycardia is suggested to improve cardiac oxygenation and adrenergic stimulation may improve cardiac contractility and protect cardiac function at high temperatures, we predicted that pharmacological blockade of cardiac autonomic control would lower CTmax. Rainbow trout was instrumented with a flow probe and a ventilation catheter for cardioventilatory recordings and exposed to an acute thermal challenge until CTmax following selective pharmacological blockade of muscarinic or β-adrenergic receptors. Contrary to our prediction, CTmax (~26°C) was unchanged between treatments. While β-adrenergic blockade reduced heart rate it did not impair cardiac stroke volume across temperatures suggesting that compensatory increases in cardiac filling pressure may serve to maintain cardiac output. While warming resulted in significant tachycardia and increased cardiac output, a high cholinergic tone on the heart was observed at temperatures approaching CTmax. This may represent a mechanism to maintain scope for heart rate and possibly to improve myocardial contractility and oxygen supply at high temperatures. This is the first study evaluating the importance of autonomic cardiac control on thermal tolerance in fish. While no effects on CTmax were observed, this study raises important questions about the underlying mechanisms determining thermal tolerance limits in ectothermic animals.
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Affiliation(s)
- Andreas Ekström
- Department of Biology and Environmental Sciences, University of Gothenburg, Gothenburg Sweden.
| | - Fredrik Jutfelt
- Department of Biology and Environmental Sciences, University of Gothenburg, Gothenburg Sweden; The Sven Lovén Centre for Marine Sciences, Kristineberg, Fiskebäckskil, Sweden
| | - Erik Sandblom
- Department of Biology and Environmental Sciences, University of Gothenburg, Gothenburg Sweden
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45
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Korajoki H, Vornanen M. Species- and chamber-specific responses of 12 kDa FK506-binding protein to temperature in fish heart. FISH PHYSIOLOGY AND BIOCHEMISTRY 2014; 40:539-549. [PMID: 24048915 DOI: 10.1007/s10695-013-9864-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 09/10/2013] [Indexed: 06/02/2023]
Abstract
The sarcoplasmic reticulum (SR) Ca(2+) release channel or ryanodine receptor (RyR) of the vertebrate heart is regulated by the FK506-binding proteins, FKBP12 and FKBP12.6. This study examines whether temperature-related changes in the SR function of fish hearts are associated with changes in FKBP12 expression. For this purpose, a polyclonal antibody against trout FKBP12 was used to compare FKPB12 expression in cold-acclimated (4 °C, CA) and warm-acclimated (18 °C, WA) rainbow trout (Oncorhynchus mykiss), burbot (Lota lota) and crucian carp (Carassius carassius) hearts. FKBP12 expression was modulated in a species- and tissue-specific manner. Temperature acclimation affected FKBP12 expression only in atrial tissue. Changes in the ventricular FKBP12 expression were not detected in any of the fish species. In the atria of rainbow trout and crucian carp, temperature acclimation produced opposite thermal responses: FKBP12 increased in the trout atrium and decreased in the crucian carp atrium under cold acclimation. In the burbot heart, chronic temperature changes did not affect cardiac FKBP12 levels. Expression of FKBP12 mRNA in rainbow trout and crucian carp hearts suggests that the transcript levels are higher in the ventricle than in the atrium and are elevated by cold acclimation in trout, but not in crucian carp. Since FKBP12 is known to increase the Ca(2+) sensitivity of cardiac RyRs and thereby the opening frequency of the Ca(2+) release channels, temperature-related changes in FKBP12 expression may modify the SR function in excitation-contraction coupling. The cold-induced increase in FKBP12 in the trout atrium and decrease in the crucian carp atrium are consistent with the previously noted increase and decrease, respectively, of SR Ca(2+) stores in cardiac contraction in these species.
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Affiliation(s)
- Hanna Korajoki
- Department of Biology, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland,
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46
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Haverinen J, Vornanen M. Effects of deltamethrin on excitability and contractility of the rainbow trout (Oncorhynchus mykiss) heart. Comp Biochem Physiol C Toxicol Pharmacol 2014; 159:1-9. [PMID: 24100050 DOI: 10.1016/j.cbpc.2013.09.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Revised: 09/19/2013] [Accepted: 09/20/2013] [Indexed: 11/24/2022]
Abstract
Pyrethroids are extensively used for the control of pest insects and disease vectors. Pyrethroid use is regarded safe due to their selective toxicity: they are effective against insects but relatively harmless to mammals and birds. Unfortunately, pyrethroids are very toxic to fishes. The high toxicity of pyrethroids to fishes is only partly explained by slow elimination rate of toxins, suggesting that high affinity binding to their molecular targets, the Na(+) channels, is involved. This study tests the hypothesis that Na(+) channels of the fish heart are targets to a type II pyrethroid, deltamethrin (DM), and therefore pyrethroids are cardiotoxic to fishes. In ventricular myocytes of the rainbow trout (Oncorhynchus mykiss) heart DM (10(-7)-3·10(-5) M) modified Na(+) current by slowing inactivation and shifting the reversal potential of the current to the left. Maximally 31±2% of the cardiac Na(+) channels were modified by DM and the half-maximal effect occurred at the concentration of 2.1 μM. The effect of DM on trout cardiac Na(+) channels is stronger and occurs about an order of magnitude lower in concentration in comparison to the orthologous mammalian Na(+) channels. In sinoatrial preparations of the trout heart DM (10 μM) caused irregularities in rate, rhythm and force of the heartbeat indicating that DM can be arrhythmogenic for the trout heart. Consistent with this, DM (>0.1 μM) induced spontaneous action potentials in otherwise quiescent ventricular myocytes. DM (10 μM) did not affect calcium current or inward rectifier and delayed rectifier potassium currents. Collectively, these findings indicate that DM exerts cardiotoxic effects in trout, and suggest that the high sensitivity of fishes to pyrethroid toxicity might be partially due to the high affinity of fish Na(+) channels to pyrethroids.
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Affiliation(s)
- Jaakko Haverinen
- University of Eastern Finland, Department of Biology, P.O. Box 111, 80101 Joensuu, Finland.
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47
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Little AG, Seebacher F. Thyroid hormone regulates cardiac performance during cold acclimation in zebrafish (Danio rerio). ACTA ACUST UNITED AC 2013; 217:718-25. [PMID: 24265422 DOI: 10.1242/jeb.096602] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Limitations to oxygen transport reduce aerobic scope and thereby activity at thermal extremes. Oxygen transport in fish is facilitated to a large extent by cardiac function so that climate variability may reduce fitness by constraining the performance of the heart. In zebrafish (Danio rerio), thyroid hormone (TH) regulates skeletal muscle function and metabolism in response to thermal acclimation. Here, we aimed to determine whether TH also regulates cardiac function during acclimation. We used propylthiouracil and iopanoic acid to induce hypothyroidism in zebrafish over a 3 week acclimation period to either 18 or 28°C. We found that cold-acclimated fish had higher maximum heart rates and sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA) activity than warm-acclimated fish. Hypothyroid treatment significantly decreased these responses in the cold-acclimated fish, but it did not affect the warm-acclimated fish. TH did not influence SERCA gene transcription, nor did it increase metabolic rate, of isolated whole hearts. To verify that physiological changes following hypothyroid treatment were in fact due to the action of TH, we supplemented hypothyroid fish with 3,5-diiodothryronine (T2) or 3,5,3'-triiodothyronine (T3). Supplementation of hypothyroid fish with T2 or T3 restored heart rate and SERCA activity to control levels. We also show that, in zebrafish, changes in cardiac output in response to warming are primarily mediated by heart rate, rather than by stroke volume. Thus, changes in heart rate are important for the overall aerobic capacity of the fish. In addition to its local effects on heart phenotype, we show that TH increases sympathetic tone on the heart at rest and during maximum exercise. Our findings reveal a new pathway through which fish can mitigate the limiting effects of temperature variability on oxygen transport to maintain aerobic scope and promote thermal tolerance.
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Affiliation(s)
- Alexander G Little
- School of Biological Sciences A08, University of Sydney, NSW 2006, Australia
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48
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Imbrogno S. The eel heart: multilevel insights into functional organ plasticity. J Exp Biol 2013; 216:3575-86. [DOI: 10.1242/jeb.089292] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Summary
The remarkable functional homogeneity of the heart as an organ requires a well-coordinated myocardial heterogeneity. An example is represented by the selective sensitivity of the different cardiac cells to physical (i.e. shear stress and/or stretch) or chemical stimuli (e.g. catecholamines, angiotensin II, natriuretic peptides, etc.), and the cell-specific synthesis and release of these substances. The biological significance of the cardiac heterogeneity has recently received great attention in attempts to dissect the complexity of the mechanisms that control the cardiac form and function. A useful approach in this regard is to identify natural models of cardiac plasticity. Among fishes, eels (genus Anguilla), for their adaptive and acclimatory abilities, represent a group of animals so far largely used to explore the structural and ultrastructural myoarchitecture organization, as well as the complex molecular networks involved in the modulation of the heart function, such as those converting environmental signals into physiological responses. However, an overview on the existing current knowledge of eel cardiac form and function is not yet available. In this context, this review will illustrate major features of eel cardiac organization and pumping performance. Aspects of autocrine–paracrine modulation and the influence of factors such as body growth, exercise, hypoxia and temperature will highlight the power of the eel heart as an experimental model useful to decipher how the cardiac morpho-functional heterogeneities may support the uniformity of the whole-organ mechanics.
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Affiliation(s)
- Sandra Imbrogno
- Department of Biology, Ecology and Earth Sciences (BEST), University of Calabria, Italy
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Vornanen M, Haverinen J, Egginton S. Acute heat tolerance of cardiac excitation in the brown trout (Salmo trutta fario). ACTA ACUST UNITED AC 2013; 217:299-309. [PMID: 24072804 DOI: 10.1242/jeb.091272] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The upper thermal tolerance and mechanisms of heat-induced cardiac failure in the brown trout (Salmo trutta fario) was examined. The point above which ion channel function and sinoatrial contractility in vitro, and electrocardiogram (ECG) in vivo, started to fail (break point temperature, BPT) was determined by acute temperature increases. In general, electrical excitation of the heart was most sensitive to heat in the intact animal (electrocardiogram, ECG) and least sensitive in isolated cardiac myocytes (ion currents). BPTs of Ca(2+) and K(+) currents of cardiac myocytes were much higher (>28°C) than BPT of in vivo heart rate (23.5 ± 0.6°C) (P<0.05). A striking exception among sarcolemmal ion conductances was the Na(+) current (INa), which was the most heat-sensitive molecular function, with a BPT of 20.9 ± 0.5°C. The low heat tolerance of INa was reflected as a low BPT for the rate of action potential upstroke in vitro (21.7 ± 1.2°C) and the velocity of impulse transmission in vivo (21.9 ± 2.2°C). These findings from different levels of biological organization strongly suggest that heat-dependent deterioration of Na(+) channel function disturbs normal spread of electrical excitation over the heart, leading to progressive variability of cardiac rhythmicity (missed beats, bursts of fast beating), reduction of heart rate and finally cessation of the normal heartbeat. Among the cardiac ion currents INa is 'the weakest link' and possibly a limiting factor for upper thermal tolerance of electrical excitation in the brown trout heart. Heat sensitivity of INa may result from functional requirements for very high flux rates and fast gating kinetics of the Na(+) channels, i.e. a trade-off between high catalytic activity and thermal stability.
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Affiliation(s)
- Matti Vornanen
- University of Eastern Finland, Department of Biology, PO Box 111, 80101 Joensuu, Finland
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Syme DA, Gamperl AK, Nash GW, Rodnick KJ. Increased ventricular stiffness and decreased cardiac function in Atlantic cod (Gadus morhua) at high temperatures. Am J Physiol Regul Integr Comp Physiol 2013; 305:R864-76. [PMID: 23883672 DOI: 10.1152/ajpregu.00055.2013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We employed the work loop method to study the ability of ventricular and atrial trabeculae from Atlantic cod to sustain power production during repeated contractions at acclimation temperatures (10°C) and when acutely warmed (20°C). Oxygen tension (Po2) was lowered from 450 to 34% air saturation to augment the thermal stress. Preparations worked under conditions simulating either a large stroke volume (35 contractions/min rate, 8-12% muscle strain) or a high heart rate (70 contractions/min, 2-4% strain), with power initially equal under both conditions. The effect of declining Po2 on power was similar under both conditions but was temperature and tissue dependent. In ventricular trabeculae at 10°C (and atria at 20°C), shortening power declined across the full range of Po2 studied, whereas the power required to lengthen the muscle was unaffected. Conversely, in ventricular trabeculae at 20°C, there was no decline in shortening power but an increase in lengthening power when Po2 fell below 100% air saturation. Finally, when ventricular trabeculae were paced at rates of up to 115 contractions/min at 20°C (vs. the maximum of 70 contractions/min in vivo), they showed marked increases in both shortening and lengthening power. Our results suggest that although elevated heart rates may not impair ventricular power as they commonly do isometric force, limited atrial power and the increased work required to expand the ventricle during diastole may compromise ventricular filling and hence, stroke volume in Atlantic cod at warm temperatures. Neither large strains nor high contraction rates convey an apparent advantage in circumventing this.
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Affiliation(s)
- Douglas A Syme
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
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