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Abramochkin DV, Filatova TS, Pustovit KB, Voronina YA, Kuzmin VS, Vornanen M. Ionic currents underlying different patterns of electrical activity in working cardiac myocytes of mammals and non-mammalian vertebrates. Comp Biochem Physiol A Mol Integr Physiol 2022; 268:111204. [PMID: 35346823 DOI: 10.1016/j.cbpa.2022.111204] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 03/21/2022] [Accepted: 03/22/2022] [Indexed: 12/19/2022]
Abstract
The orderly contraction of the vertebrate heart is determined by generation and propagation of cardiac action potentials (APs). APs are generated by the integrated activity of time- and voltage-dependent ionic channels which carry inward Na+ and Ca2+ currents, and outward K+ currents. This review compares atrial and ventricular APs and underlying ion currents between different taxa of vertebrates. We have collected literature data and attempted to find common electrophysiological features for two or more vertebrate groups, show differences between taxa and cardiac chambers, and indicate gaps in the existing data. Although electrical excitability of the heart in all vertebrates is based on the same superfamily of channels, there is a vast variability of AP waveforms between atrial and ventricular myocytes, between different species of the same vertebrate class and between endothermic and ectothermic animals. The wide variability of AP shapes is related to species-specific differences in animal size, heart rate, stage of ontogenetic development, excitation-contraction coupling, temperature and oxygen availability. Some of the differences between taxa are related to evolutionary development of genomes, which appear e.g. in the expression of different Na+ and K+ channel orthologues in cardiomyocytes of vertebrates. There is a wonderful variability of AP shapes and underlying ion currents with which electrical excitability of vertebrate heart can be generated depending on the intrinsic and extrinsic conditions of animal body. This multitude of ionic mechanisms provides excellent material for studying how the function of the vertebrate heart can adapt or acclimate to prevailing physiological and environmental conditions.
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Affiliation(s)
- Denis V Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow 119234, Russia.
| | - Tatiana S Filatova
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow 119234, Russia
| | - Ksenia B Pustovit
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow 119234, Russia
| | - Yana A Voronina
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow 119234, Russia; Laboratory of Cardiac Electrophysiology, National Medical Research Center for Cardiology, 3(rd) Cherepkovskaya str., 15A, Moscow, Russia
| | - Vladislav S Kuzmin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow 119234, Russia; Department of Physiology, Pirogov Russian National Research Medical University, Ostrovityanova str., 1, Moscow, Russia
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
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2
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Lou F, Liu M, Han Z, Gao T. Comparative transcriptome reveals the thermal stress response differences between Heilongjiang population and Xinjiang population of Lota lota. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART D, GENOMICS & PROTEOMICS 2022; 42:100960. [PMID: 35042124 DOI: 10.1016/j.cbd.2022.100960] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 12/24/2021] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
Some cold-water fishes are particularly sensitive to the water temperature increasing caused by current global warming. However, the alterations in the physiology and behavior of infraspecific populations living in heterogeneous landscapes in response to water temperature increasing were significantly different. Consequently, understanding the impact of temperature increasing on different populations may be crucial for the conservation of cold-water fishes in the context of global warming. The burbot is the only freshwater specie in Gadiformes. To better understand the differences of different populations of burbot under similar thermal stress, Lota lota was selected as the research objects. Firstly, RNA-seq was applied to identify the transcriptomic responses of Heilongjiang population exposed to three temperature gradients (0 °C, 18 °C and 28 °C). Compared with 0 °C, 4216 and 12,657 genes were significantly differentially expressed at 18 °C and 28 °C, respectively. Meanwhile, 49 genes were significantly differentially expressed in three temperature pairs and these genes were presumed to involve in stress response process, immunologic process, reproductive process, development process, material metabolism process, signal transduction process, spermatogenesis process and cell apoptosis process. The response differences of two L. lota populations to similar thermal stress were compared and the results showed that they have different gene expression responses (the number of differentially expression genes and biological processes). The lower annual temperature of the Heilongjiang River might make it more sensitive to temperature increasing. Based on the comparative transcriptome analyses, 12 orthologous genes were considered as the potential regulators of L. lota preference for cold-water environment and these genes are potentially related to the immunologic process, reproductive process, development process, signal transduction process, and cell apoptosis process. Those results can provide basic information for the rational development of conservation strategies of different L. lota populations under the background of global warming.
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Affiliation(s)
- Fangrui Lou
- School of Ocean, Yantai University, Yantai, Shandong 264005, China
| | - Manhong Liu
- College of Wildlife and Protected Areas, Northeast Forestry University, Harbin, Heilongjiang 150040, China
| | - Zhiqiang Han
- Fishery College, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, China
| | - Tianxiang Gao
- Fishery College, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, China.
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3
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Stecyk JAW, Couturier CS, Abramochkin DV, Hall D, Arrant-Howell A, Kubly KL, Lockmann S, Logue K, Trueblood L, Swalling C, Pinard J, Vogt A. Cardiophysiological responses of the air-breathing Alaska blackfish to cold acclimation and chronic hypoxic submergence at 5°C. J Exp Biol 2020; 223:jeb225730. [PMID: 33020178 PMCID: PMC7687868 DOI: 10.1242/jeb.225730] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 09/28/2020] [Indexed: 01/29/2023]
Abstract
The Alaska blackfish (Dallia pectoralis) remains active at cold temperatures when experiencing aquatic hypoxia without air access. To discern the cardiophysiological adjustments that permit this behaviour, we quantified the effect of acclimation from 15°C to 5°C in normoxia (15N and 5N fish), as well as chronic hypoxic submergence (6-8 weeks; ∼6.3-8.4 kPa; no air access) at 5°C (5H fish), on in vivo and spontaneous heart rate (fH), electrocardiogram, ventricular action potential (AP) shape and duration (APD), the background inward rectifier (IK1) and rapid delayed rectifier (IKr) K+ currents and ventricular gene expression of proteins involved in excitation-contraction coupling. In vivo fH was ∼50% slower in 5N than in 15N fish, but 5H fish did not display hypoxic bradycardia. Atypically, cold acclimation in normoxia did not induce shortening of APD or alter resting membrane potential. Rather, QT interval and APD were ∼2.6-fold longer in 5N than in 15N fish because outward IK1 and IKr were not upregulated in 5N fish. By contrast, chronic hypoxic submergence elicited a shortening of QT interval and APD, driven by an upregulation of IKr The altered electrophysiology of 5H fish was accompanied by increased gene expression of kcnh6 (3.5-fold; Kv11.2 of IKr), kcnj12 (7.4-fold; Kir2.2 of IK1) and kcnj14 (2.9-fold; Kir2.4 of IK1). 5H fish also exhibited a unique gene expression pattern that suggests modification of ventricular Ca2+ cycling. Overall, the findings reveal that Alaska blackfish exposed to chronic hypoxic submergence prioritize the continuation of cardiac performance to support an active lifestyle over reducing cardiac ATP demand.
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Affiliation(s)
- Jonathan A W Stecyk
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
| | - Christine S Couturier
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
| | - Denis V Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, 1-12 Leninskiye Gory, 119991 Moscow, Russia
- Ural Federal University, 19 Mira Street, 620002 Ekaterinburg, Russia
- Laboratory of Cardiac Physiology, Institute of Physiology of Kоmi Science Centre of the Ural Branch of the Russian Academy of Sciences, FRC Komi SC UB RAS, 50 Pervomayskaya Str., 167982 Syktyvkar, Komi Republic, Russia
| | - Diarmid Hall
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
| | - Asia Arrant-Howell
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
| | - Kerry L Kubly
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
| | - Shyanne Lockmann
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
| | - Kyle Logue
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
| | - Lenett Trueblood
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
| | - Connor Swalling
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
| | - Jessica Pinard
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
| | - Angela Vogt
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
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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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5
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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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6
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Abramochkin DV, Haverinen J, Mitenkov YA, Vornanen M. Temperature- and external K+-dependence of electrical excitation in ventricular myocytes of cod-like fishes. J Exp Biol 2019; 222:jeb.193607. [DOI: 10.1242/jeb.193607] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 01/16/2019] [Indexed: 01/08/2023]
Abstract
Electrical excitability (EE) is vital for cardiac function and strongly modulated by temperature and external K+ concentration ([K+]o) as formulated in the hypothesis of temperature-dependent deterioration of electrical excitability (TDEE). Since little is known about EE of arctic stenothermic fishes, we tested the TDEE hypothesis on ventricular myocytes of polar cod (Boreogadus saida) and navaga cod (Eleginus navaga) of the Arctic Ocean and those of temperate freshwater burbot (Lota lota). Ventricular action potentials (APs) were elicited in current-clamp experiments at 3, 9 and 15°C, and AP characteristics and the current needed to elicit AP were examined. At 3°C, ventricular APs of polar and navaga cod were similar but differed from that of burbot in having lower rate of AP upstroke and higher rate of repolarization. EE of ventricular myocytes - defined as the ease with which all-or-none APs are triggered - was little affected by acute temperature changes between 3 and 15°C in any species. However, AP duration (APD50) was drastically reduced at higher temperatures. Elevation of [K+]o from 3 to 5.4 and further to 8 mM at 3, 9 and 15°C strongly affected EE and AP characteristics in polar and navaga cod, but less in burbot. In all species, ventricular excitation was resistant to acute temperature elevations, while small increases in [K+]o severely compromised EE, in particular in the marine stenotherms. This suggests that EE of the heart in these Gadiformes species is well equipped against acute warming, but less so against the simultaneous temperature and exercise stresses.
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Affiliation(s)
- Denis V. Abramochkin
- Department of human and animal physiology, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia
- Department of Physiology, Pirogov Russian National Research Medical University, Moscow, Russia
- Laboratory of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Russia
| | - Jaakko Haverinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Yuri A. Mitenkov
- VNIRO Russian Federal Research Institute of Fisheries and Oceanography, Moscow, Russia
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
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7
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Haverinen J, Hassinen M, Dash SN, Vornanen M. Expression of calcium channel transcripts in the zebrafish heart: dominance of T-type channels. ACTA ACUST UNITED AC 2018; 221:jeb.179226. [PMID: 29739832 DOI: 10.1242/jeb.179226] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 04/06/2018] [Indexed: 12/13/2022]
Abstract
Calcium channels are necessary for cardiac excitation-contraction (E-C) coupling, but Ca2+ channel composition of fish hearts is still largely unknown. To this end, we determined transcript expression of Ca2+ channels in the heart of zebrafish (Danio rerio), a popular model species. Altogether, 18 Ca2+ channel α-subunit genes were expressed in both atrium and ventricle. Transcripts for 7 L-type (Cav1.1a, Cav1.1b, Cav1.2, Cav1.3a, Cav1.3b, Cav1.4a, Cav1.4b), 5 T-type (Cav3.1, Cav3.2a, Cav3.2b, Cav3.3a, Cav3.3b) and 6 P/Q-, N- and R-type (Cav2.1a, Cav2.1b, Cav2.2a, Cav2.2b, Cav2.3a, Cav2.3b) Ca2+ channels were expressed. In the ventricle, T-type channels formed 54.9%, L-type channels 41.1% and P/Q-, N- and R-type channels 4.0% of the Ca2+ channel transcripts. In the atrium, the relative expression of T-type and L-type Ca2+ channel transcripts was 64.1% and 33.8%, respectively (others accounted for 2.1%). Thus, at the transcript level, T-type Ca2+ channels are prevalent in zebrafish atrium and ventricle. At the functional level, peak densities of ventricular T-type (ICaT) and L-type (ICaL) Ca2+ current were 6.3±0.8 and 7.7±0.8 pA pF-1, respectively. ICaT mediated a sizeable sarcolemmal Ca2+ influx into ventricular myocytes: the increment in total cellular Ca2+ content via ICaT was 41.2±7.3 µmol l-1, which was 31.7% of the combined Ca2+ influx (129 µmol l-1) via ICaT and ICaL (88.5±20.5 µmol l-1). The diversity of expressed Ca2+ channel genes in zebrafish heart is high, but dominated by the members of the T-type subfamily. The large ventricular ICaT is likely to play a significant role in E-C coupling.
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Affiliation(s)
- Jaakko Haverinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Minna Hassinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Surjya Narayan Dash
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland.,Neuroscience Center and Department of Anatomy, Faculty of Medicine, University of Helsinki, PO Box 63, 00014 Helsinki, Finland
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
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Rissoli RZ, Vasconcelos EDS, Rantin FT, Kalinin AL. Effects of exercise training on excitation-contraction coupling, calcium dynamics and protein expression in the heart of the Neotropical fish Brycon amazonicus. Comp Biochem Physiol A Mol Integr Physiol 2017; 214:85-93. [PMID: 28966144 DOI: 10.1016/j.cbpa.2017.09.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 09/21/2017] [Accepted: 09/21/2017] [Indexed: 10/18/2022]
Abstract
Matrinxã (Brycon amazonicus) is a great swimming performance teleost fish from the Amazon basin. However, the possible cardiac adaptations of this ability are still unknown. Therefore, the aim of the present work was to investigate the effects of prolonged exercise (EX group - 60days under 0.4BL·s-1) on ventricular contractility by (i) in-vitro analysis of contractility comparing the relative roles of sodium/calcium exchanger (NCX) and sarcoplasmic reticulum (SR) in the excitation-contraction (E-C) coupling and (ii) molecular analysis of NCX, sarcoplasmic reticulum Ca2+ ATPase (SERCA2) and phospholamban (PLB) expression and quantification. The exercise training significantly improved twitch tension, cardiac pumping capacity and the contraction rate when compared to controls (CT). Inhibition of the NCX function, replacing Na+ by Li+ in the physiological solutions, diminished cardiac contractility in the EX group, reduced all analyzed parameters under both high and low stimulation frequencies. The SR blockage, using 10μM ryanodine, caused ~50% tension reduction in CT at most analyzed frequencies while in EX, reductions (34-54%) were only found at higher frequencies. SR inhibition also decreased contraction and relaxation rates in both groups. Additionally, higher post-rest contraction values were recorded for EX, indicating an increase in SR Ca2+ loading. Higher NCX and PLB expression rates and lower SERCA2 rates were found in EX. Our data indicate that matrinxã presents a modulation in E-C coupling after exercise-training, enhancing the SR function under higher frequencies. This was the first study to functionally analyze the effects of swimming-induced exercise on fish cardiac E-C coupling.
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Affiliation(s)
- Rafael Zanelli Rissoli
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, SP, Brazil
| | | | - Francisco Tadeu Rantin
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, SP, Brazil
| | - Ana Lúcia Kalinin
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, SP, Brazil.
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9
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Vornanen M. Electrical Excitability of the Fish Heart and Its Autonomic Regulation. FISH PHYSIOLOGY 2017. [DOI: 10.1016/bs.fp.2017.04.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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10
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Keen AN, Klaiman JM, Shiels HA, Gillis TE. Temperature-induced cardiac remodelling in fish. ACTA ACUST UNITED AC 2016; 220:147-160. [PMID: 27852752 PMCID: PMC5278617 DOI: 10.1242/jeb.128496] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Thermal acclimation causes the heart of some fish species to undergo significant remodelling. This includes changes in electrical activity, energy utilization and structural properties at the gross and molecular level of organization. The purpose of this Review is to summarize the current state of knowledge of temperature-induced structural remodelling in the fish ventricle across different levels of biological organization, and to examine how such changes result in the modification of the functional properties of the heart. The structural remodelling response is thought to be responsible for changes in cardiac stiffness, the Ca2+ sensitivity of force generation and the rate of force generation by the heart. Such changes to both active and passive properties help to compensate for the loss of cardiac function caused by a decrease in physiological temperature. Hence, temperature-induced cardiac remodelling is common in fish that remain active following seasonal decreases in temperature. This Review is organized around the ventricular phases of the cardiac cycle – specifically diastolic filling, isovolumic pressure generation and ejection – so that the consequences of remodelling can be fully described. We also compare the thermal acclimation-associated modifications of the fish ventricle with those seen in the mammalian ventricle in response to cardiac pathologies and exercise. Finally, we consider how the plasticity of the fish heart may be relevant to survival in a climate change context, where seasonal temperature changes could become more extreme and variable. Summary: Thermal acclimation of some temperate fishes causes extensive remodelling of the heart. The resultant changes to the active and passive properties of the heart represent a highly integrated phenotypic response.
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Affiliation(s)
- Adam N Keen
- Division of Cardiovascular Science, School of Medicine, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9NT, UK
| | - Jordan M Klaiman
- Department of Rehabilitation Medicine, University of Washington, Seattle, WA 98109, USA
| | - Holly A Shiels
- Division of Cardiovascular Science, School of Medicine, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9NT, UK
| | - Todd E Gillis
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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11
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Shiels HA, Galli GLJ, Block BA. Cardiac function in an endothermic fish: cellular mechanisms for overcoming acute thermal challenges during diving. Proc Biol Sci 2016; 282:20141989. [PMID: 25540278 DOI: 10.1098/rspb.2014.1989] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Understanding the physiology of vertebrate thermal tolerance is critical for predicting how animals respond to climate change. Pacific bluefin tuna experience a wide range of ambient sea temperatures and occupy the largest geographical niche of all tunas. Their capacity to endure thermal challenge is due in part to enhanced expression and activity of key proteins involved in cardiac excitation-contraction coupling, which improve cardiomyocyte function and whole animal performance during temperature change. To define the cellular mechanisms that enable bluefin tuna hearts to function during acute temperature change, we investigated the performance of freshly isolated ventricular myocytes using confocal microscopy and electrophysiology. We demonstrate that acute cooling and warming (between 8 and 28°C) modulates the excitability of the cardiomyocyte by altering the action potential (AP) duration and the amplitude and kinetics of the cellular Ca(2+) transient. We then explored the interactions between temperature, adrenergic stimulation and contraction frequency, and show that when these stressors are combined in a physiologically relevant way, they alter AP characteristics to stabilize excitation-contraction coupling across an acute 20°C temperature range. This allows the tuna heart to maintain consistent contraction and relaxation cycles during acute thermal challenges. We hypothesize that this cardiac capacity plays a key role in the bluefin tunas' niche expansion across a broad thermal and geographical range.
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Affiliation(s)
- H A Shiels
- Faculty of Life Sciences, The University of Manchester, Core Technology Facility, Grafton Street, Manchester M13 9PL, UK
| | - G L J Galli
- Faculty of Medical and Human Sciences, The University of Manchester, Core Technology Facility, Grafton Street, Manchester M13 9PL, UK
| | - B A Block
- Department of Biology, Tuna Research and Conservation Center, Stanford University, 120 Oceanview Boulevard, Pacific Grove, CA 93950, USA
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12
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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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13
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Kubly KL, Stecyk JAW. Temperature-dependence of L-type Ca(2+) current in ventricular cardiomyocytes of the Alaska blackfish (Dallia pectoralis). J Comp Physiol B 2015; 185:845-58. [PMID: 26439127 DOI: 10.1007/s00360-015-0931-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 08/04/2015] [Accepted: 09/07/2015] [Indexed: 01/12/2023]
Abstract
To lend insight into the overwintering strategy of the Alaska blackfish (Dallia pectoralis), we acclimated fish to 15 or 5 °C and then utilized whole-cell patch clamp to characterize the effects of thermal acclimation and acute temperature change on the density and kinetics of ventricular L-type Ca(2+) current (I Ca). Peak I Ca density at 5 °C (-1.1 ± 0.1 pA pF(-1)) was 1/8th that at 15 °C (-8.8 ± 0.6 pA pF(-1)). However, alterations of the Ca(2+)- and voltage-dependent inactivation properties of L-type Ca(2+) channels partially compensated against the decrease. The time constant tau (τ) for the kinetics of inactivation of I Ca was ~4.5 times greater at 5 °C than at 15 °C, and the voltage for half-maximal inactivation was shifted from -23.3 ± 1.0 mV at 15 °C to -19.8 ± 1.2 mV at 5 °C. These modifications increase the open probability of the channel and culminate in an approximate doubling of the L-type Ca(2+) window current, which contributes to approximately 15% of the maximal Ca(2+) conductance at 5 °C. Consequently, the charge density of I Ca (Q Ca) and the total Ca(2+) transferred through the L-type Ca(2+) channels (Δ[Ca(2+)]) were not as severely reduced at 5 °C as compared to peak I Ca density. In combination, the results suggest that while the Alaska blackfish substantially down-regulates I Ca with acclimation to low temperature, there is sufficient compensation in the kinetics of the L-type Ca(2+) channel to support the level of cardiac performance required for the fish to remain active throughout the winter.
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Affiliation(s)
- Kerry L Kubly
- Department of Biological Sciences, University of Alaska Anchorage, 3211 Providence Drive, Conoco Philips Integrated Science Building, Anchorage, AK, 99508, USA.
| | - Jonathan A W Stecyk
- Department of Biological Sciences, University of Alaska Anchorage, 3211 Providence Drive, Conoco Philips Integrated Science Building, Anchorage, AK, 99508, USA
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14
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Shiels HA, Galli GL. The Sarcoplasmic Reticulum and the Evolution of the Vertebrate Heart. Physiology (Bethesda) 2014; 29:456-69. [DOI: 10.1152/physiol.00015.2014] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The sarcoplasmic reticulum (SR) is crucial for contraction and relaxation of the mammalian cardiomyocyte, but its role in other vertebrate classes is equivocal. Recent evidence suggests differences in SR function across species may have an underlying structural basis. Here, we discuss how SR recruitment relates to the structural organization of the cardiomyocyte to provide new insight into the evolution of cardiac design and function in vertebrates.
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Affiliation(s)
- Holly A. Shiels
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom; and
| | - Gina L.J. Galli
- Faculty of Medical and Human Sciences, University of Manchester, Manchester, United Kingdom
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15
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Haverinen J, Egginton S, Vornanen M. Electrical Excitation of the Heart in a Basal Vertebrate, the European River Lamprey (Lampetra fluviatilis). Physiol Biochem Zool 2014; 87:817-28. [DOI: 10.1086/678954] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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16
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Ballesta S, Hanson LM, Farrell AP. The effect of adrenaline on the temperature dependency of cardiac action potentials in pink salmon Oncorhynchus gorbuscha. JOURNAL OF FISH BIOLOGY 2012; 80:876-885. [PMID: 22471806 DOI: 10.1111/j.1095-8649.2011.03187.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Using sharp electrode impalement, action potentials recorded from atrial and ventricular tissue of pink salmon Oncorhynchus gorbuscha generally decreased in duration with increasing test temperature (6, 10, 16 and 20° C). Stimulation of the tissue using 500 nM adrenaline had no significant effect on the duration of the atrial action potential at any test temperature but lengthened the ventricular action potential by ~17%.
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Affiliation(s)
- S Ballesta
- University of British Columbia, 2357 Main Mall, Vancouver, BC, V6T 1Z4 Canada.
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17
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Lurman GJ, Petersen LH, Gamperl AK. Atlantic cod (Gadus morhua L.) in situ cardiac performance at cold temperatures: long-term acclimation, acute thermal challenge and the role of adrenaline. J Exp Biol 2012; 215:4006-14. [DOI: 10.1242/jeb.069849] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Summary
The resting and maximum in situ cardiac performance of Newfoundland Atlantic cod (Gadus morhua L.) acclimated to 10, 4 and 0°C were measured at their respective acclimation temperatures, and when acutely exposed to temperature changes: i.e. hearts from 10°C fish cooled to 4°C, and hearts from 4°C fish measured at 10°C and 0°C. Intrinsic heart rate (fH) decreased from 41 beats min-1 (bpm) at 10°C to 33 bpm at 4°C and to 25 bpm at 0°C. However, this degree of thermal dependency was not reflected in maximal cardiac output. Qmax values were ~44, ~37 and ~34 ml min-1 kg-1 at 10, 4 and 0°C, respectively. Further, cardiac scope showed a slight positive compensation between 4 and 0°C (Q10 = 1.7), and full, if not a slight over compensation between 10 and 4°C (Q10 = 0.9). The maximal performance of hearts exposed to an acute decrease in temperature (i.e. from 10°C to 4°C and 4°C to 0°C) was comparable to that measured for hearts from 4 and 0°C acclimated fish, respectively. In contrast, 4°C acclimated hearts significantly out-performed 10°C acclimated hearts when tested at a common temperature of 10°C (in terms of both Qmax and power output). Only minimal differences in cardiac function were seen between hearts stimulated with basal (5 nM) vs. maximal (200 nM) levels of adrenaline, the effects of which were not temperature dependant. These results: 1) show that maximum performance of the isolated cod heart is not compromised by exposure to cold temperatures; and 2) support data from other studies which show that, in contrast to salmonids, cod cardiac performance/myocardial contractility is not dependent upon humoral adrenergic stimulation.
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18
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Galli GLJ, Lipnick MS, Shiels HA, Block BA. Temperature effects on Ca2+ cycling in scombrid cardiomyocytes: a phylogenetic comparison. ACTA ACUST UNITED AC 2011; 214:1068-76. [PMID: 21389190 DOI: 10.1242/jeb.048231] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Specialisations in excitation-contraction coupling may have played an important role in the evolution of endothermy and high cardiac performance in scombrid fishes. We examined aspects of Ca(2+) handling in cardiomyocytes from Pacific bonito (Sarda chiliensis), Pacific mackerel (Scomber japonicus), yellowfin tuna (Thunnus albacares) and Pacific bluefin tuna (Thunnus orientalis). The whole-cell voltage-clamp technique was used to measure the temperature sensitivity of the L-type Ca(2+) channel current (I(Ca)), density, and steady-state and maximal sarcoplasmic reticulum (SR) Ca(2+) content (ssSR(load) and maxSR(load)). Current-voltage relations, peak I(Ca) density and charge density of I(Ca) were greatest in mackerel and yellowfin at all temperatures tested. I(Ca) density and kinetics were temperature sensitive in all species studied, and the magnitude of this response was not related to the thermal preference of the species. SR(load) was greater in atrial than in ventricular myocytes in the Pacific bluefin tuna, and in species that are more cold tolerant (bluefin tuna and mackerel). I(Ca) and SR(load) were particularly small in bonito, suggesting the Na(+)/Ca(2+) exchanger plays a more pivotal role in Ca(2+) entry into cardiomyocytes of this species. Our comparative approach reveals that the SR of cold-tolerant scombrid fishes has a greater capacity for Ca(2+) storage. This specialisation may contribute to the temperature tolerance and thermal niche expansion of the bluefin tuna and mackerel.
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Affiliation(s)
- Gina L J Galli
- Hopkins Marine Station of Stanford University, 120 Oceanview Boulevard, Pacific Grove, CA 93950, USA.
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19
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Zhang PC, Llach A, Sheng XY, Hove-Madsen L, Tibbits GF. Calcium handling in zebrafish ventricular myocytes. Am J Physiol Regul Integr Comp Physiol 2010; 300:R56-66. [PMID: 20926764 DOI: 10.1152/ajpregu.00377.2010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The zebrafish is an important model for the study of vertebrate cardiac development with a rich array of genetic mutations and biological reagents for functional interrogation. The similarity of the zebrafish (Danio rerio) cardiac action potential with that of humans further enhances the relevance of this model. In spite of this, little is known about excitation-contraction coupling in the zebrafish heart. To address this issue, adult zebrafish cardiomyocytes were isolated by enzymatic perfusion of the cannulated ventricle and were subjected to amphotericin-perforated patch-clamp technique, confocal calcium imaging, and/or measurements of cell shortening. Simultaneous recordings of the voltage dependence of the L-type calcium current (I(Ca,L)) amplitude and cell shortening showed a typical bell-shaped current-voltage (I-V) relationship for I(Ca,L) with a maximum at +10 mV, whereas calcium transients and cell shortening showed a monophasic increase with membrane depolarization that reached a plateau at membrane potentials above +20 mV. Values of I(Ca,L) were 53, 100, and 17% of maximum at -20, +10, and +40 mV, while the corresponding calcium transient amplitudes were 64, 92, and 98% and cell shortening values were 62, 95, and 96% of maximum, respectively, suggesting that I(Ca,L) is the major contributor to the activation of contraction at voltages below +10 mV, whereas the contribution of reverse-mode Na/Ca exchange becomes increasingly more important at membrane potentials above +10 mV. Comparison of the recovery of I(Ca,L) from acute and steady-state inactivation showed that reduction of I(Ca,L) upon elevation of the stimulation frequency is primarily due to calcium-dependent I(Ca,L) inactivation. In conclusion, we demonstrate that a large yield of healthy atrial and ventricular myocytes can be obtained by enzymatic perfusion of the cannulated zebrafish heart. Moreover, zebrafish ventricular myocytes differed from that of large mammals by having larger I(Ca,L) density and a monophasically increasing contraction-voltage relationship, suggesting that caution should be taken upon extrapolation of the functional impact of mutations on calcium handling and contraction in zebrafish cardiomyocytes.
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20
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Shiels HA, Di Maio A, Thompson S, Block BA. Warm fish with cold hearts: thermal plasticity of excitation-contraction coupling in bluefin tuna. Proc Biol Sci 2010; 278:18-27. [PMID: 20667881 DOI: 10.1098/rspb.2010.1274] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Bluefin tuna have a unique physiology. Elevated metabolic rates coupled with heat exchangers enable bluefin tunas to conserve heat in their locomotory muscle, viscera, eyes and brain, yet their hearts operate at ambient water temperature. This arrangement of a warm fish with a cold heart is unique among vertebrates and can result in a reduction in cardiac function in the cold despite the elevated metabolic demands of endothermic tissues. In this study, we used laser scanning confocal microscopy and electron microscopy to investigate how acute and chronic temperature change affects tuna cardiac function. We examined the temporal and spatial properties of the intracellular Ca2+ transient (Δ[Ca2+]i) in Pacific bluefin tuna (Thunnus orientalis) ventricular myocytes at the acclimation temperatures of 14°C and 24°C and at a common test temperature of 19°C. Acute (less than 5 min) warming and cooling accelerated and slowed the kinetics of Δ[Ca2+]i, indicating that temperature change limits cardiac myocyte performance. Importantly, we show that thermal acclimation offered partial compensation for these direct effects of temperature. Prolonged cold exposure (more than four weeks) increased the amplitude and kinetics of Δ[Ca2+]i by increasing intracellular Ca2+ cycling through the sarcoplasmic reticulum (SR). These functional findings are supported by electron microscopy, which revealed a greater volume fraction of ventricular SR in cold-acclimated tuna myocytes. The results indicate that SR function is crucial to the performance of the bluefin tuna heart in the cold. We suggest that SR Ca2+ cycling is the malleable unit of cellular Ca2+ flux, offering a mechanism for thermal plasticity in fish hearts. These findings have implications beyond endothermic fish and may help to delineate the key steps required to protect vertebrate cardiac function in the cold.
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Affiliation(s)
- H A Shiels
- Faculty of Life Sciences, The University of Manchester, Core Technology Facility, Grafton Street, Manchester M13 9PL, UK.
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21
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Galli GLJ, Warren DE, Shiels HA. Ca2+ cycling in cardiomyocytes from a high-performance reptile, the varanid lizard (Varanus exanthematicus). Am J Physiol Regul Integr Comp Physiol 2009; 297:R1636-44. [PMID: 19812356 PMCID: PMC2803631 DOI: 10.1152/ajpregu.00381.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The varanid lizard possesses one of the largest aerobic capacities among reptiles with maximum rates of oxygen consumption that are twice that of other lizards of comparable sizes at the same temperature. To support this aerobic capacity, the varanid heart possesses morphological adaptations that allow the generation of high heart rates and blood pressures. Specializations in excitation-contraction coupling may also contribute to the varanids superior cardiovascular performance. Therefore, we investigated the electrophysiological properties of the l-type Ca(2+) channel and the Na(+)/Ca(2+) exchanger (NCX) and the contribution of the sarcoplasmic reticulum to the intracellular Ca(2+) transient (Delta[Ca(2+)](i)) in varanid lizard ventricular myocytes. Additionally, we used confocal microscopy to visualize myocytes and make morphological measurements. Lizard ventricular myocytes were found to be spindle-shaped, lack T-tubules, and were approximately 190 microm in length and 5-7 microm in width and depth. Cardiomyocytes had a small cell volume ( approximately 2 pL), leading to a large surface area-to-volume ratio (18.5), typical of ectothermic vertebrates. The voltage sensitivity of the l-type Ca(2+) channel current (I(Ca)), steady-state activation and inactivation curves, and the time taken for recovery from inactivation were also similar to those measured in other reptiles and teleosts. However, transsarcolemmal Ca(2+) influx via reverse mode Na(+)/Ca(2+) exchange current was fourfold higher than most other ectotherms. Moreover, pharmacological inhibition of the sarcoplasmic reticulum led to a 40% reduction in the Delta[Ca(2+)](i) amplitude, and slowed the time course of decay. In aggregate, our results suggest varanids have an enhanced capacity to transport Ca(2+) through the Na(+)/Ca(2+) exchanger, and sarcoplasmic reticulum suggesting specializations in excitation-contraction coupling may provide a means to support high cardiovascular performance.
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Affiliation(s)
- Gina L J Galli
- Faculty of Life Sciences, The University of Manchester, Core Technology Facility, Manchester, United Kingdom.
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22
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Birkedal R, Christopher J, Thistlethwaite A, Shiels HA. Temperature acclimation has no effect on ryanodine receptor expression or subcellular localization in rainbow trout heart. J Comp Physiol B 2009; 179:961-9. [DOI: 10.1007/s00360-009-0377-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Revised: 05/29/2009] [Accepted: 06/02/2009] [Indexed: 11/30/2022]
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23
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Pörtner HO, Lannig G. Chapter 4 Oxygen and Capacity Limited Thermal Tolerance. FISH PHYSIOLOGY 2009. [DOI: 10.1016/s1546-5098(08)00004-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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Stecyk JAW, Galli GL, Shiels HA, Farrell AP. Cardiac survival in anoxia-tolerant vertebrates: An electrophysiological perspective. Comp Biochem Physiol C Toxicol Pharmacol 2008; 148:339-54. [PMID: 18589002 DOI: 10.1016/j.cbpc.2008.05.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Revised: 05/31/2008] [Accepted: 05/31/2008] [Indexed: 11/24/2022]
Abstract
Certain vertebrates, such as freshwater turtles of the genus Chrysemys and Trachemys and crucian carp (Carassius carassius), have anoxia-tolerant hearts that continue to function throughout prolonged periods of anoxia (up to many months) due to successful balancing of cellular ATP supply and demand. In the present review, we summarize the current and limited understanding of the cellular mechanisms underlying this cardiac anoxia tolerance. What emerges is that cold temperature substantially modifies cardiac electrophysiology to precondition the heart for winter anoxia. Intrinsic heart rate is slowed and density of sarcolemmal ion currents substantially modified to alter cardiac action potential (AP) characteristics. These changes depress cardiac activity and reduce the energetic costs associated with ion pumping. In contrast, anoxia per se results in limited changes to cardiac AP shape or ion current densities in turtle and crucian carp, suggesting that anoxic modifications of cardiac electrophysiology to reduce ATP demand are not extensive. Additionally, as knowledge of cellular physiology in non-mammalian vertebrates is still in its infancy, we briefly discuss the cellular defense mechanisms towards the acidosis that accompanies anoxia as well as mammalian cardiac models of hypoxia/ischemia tolerance. By examining if fundamental cellular mechanisms have been conserved during the evolution of anoxia tolerance we hope to have provided a framework for the design of future experiments investigating cardiac cellular mechanisms of anoxia survival.
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Affiliation(s)
- Jonathan A W Stecyk
- Physiology Programme, Department of Molecular Biosciences, University of Oslo, PO Box 1041, N-0316, Oslo, Norway.
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25
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Ultrastructure of the sarcoplasmic reticulum in cardiac myocytes from Pacific bluefin tuna. Cell Tissue Res 2008; 334:121-34. [DOI: 10.1007/s00441-008-0669-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2008] [Accepted: 07/01/2008] [Indexed: 10/21/2022]
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26
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Abstract
Intracellular Na+-concentration, [Na+]i modulates excitation-contraction coupling of cardiac myocytes via the Na+/Ca2+ exchanger (NCX). In cardiomyocytes from rainbow trout ( Oncorhyncus mykiss), whole cell patch-clamp studies have shown that Ca2+ influx via reverse-mode NCX contributes significantly to contraction when [Na+]i is 16 mM but not 10 mM. However, physiological [Na+]i has never been measured. We recorded [Na+]i using the fluorescent indicator sodium-binding benzofuran isophthalate in freshly isolated atrial and ventricular myocytes from rainbow trout. We examined [Na+]i at rest and during increases in contraction frequency across three temperatures that span those trout experience in nature (7, 14, and 21°C). Surprisingly, we found that [Na+]i was not different between atrial and ventricular cells. Furthermore, acute temperature changes did not affect [Na+]i in resting cells. Thus, we report a resting in vivo [Na+]i of 13.4 mM for rainbow trout cardiomyocytes. [Na+]i increased from rest with increases in contraction frequency by 3.2, 4.7, and 6.5% at 0.2, 0.5, and 0.8 Hz, respectively. This corresponds to an increase of 0.4, 0.6, and 0.9 mM at 0.2, 0.5, and 0.8 Hz, respectively. Acute temperature change did not significantly affect the contraction-induced increase in [Na+]i. Our results provide the first measurement of [Na+]i in rainbow trout cardiomyocytes. This surprisingly high [Na+]i is likely to result in physiologically significant Ca2+ influx via reverse-mode NCX during excitation-contraction coupling. We calculate that this Ca2+-source will decrease with the action potential duration as temperature and contraction frequency increases.
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Affiliation(s)
- Rikke Birkedal
- Faculty of Life Sciences, The University of Manchester, Core Technology Facility, Second Floor, 46 Grafton St., Manchester M13 9NT, United Kingdom.
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27
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Stecyk JAW, Paajanen V, Farrell AP, Vornanen M. Effect of temperature and prolonged anoxia exposure on electrophysiological properties of the turtle (Trachemys scripta) heart. Am J Physiol Regul Integr Comp Physiol 2007; 293:R421-37. [PMID: 17442785 DOI: 10.1152/ajpregu.00096.2007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiac activity of the turtle (Trachemys scripta) is greatly depressed with cold acclimation and anoxia. We examined what electrophysiological modifications accompany and perhaps facilitate this depression of cardiac activity. Turtles were first acclimated to 21 degrees C or 5 degrees C and held under either normoxic or anoxic (6 h at 21 degrees C; 14 days at 5 degrees C) conditions. We then measured cardiac action potentials (APs) using spontaneously contracting whole heart preparations and whole cell current densities of sarcolemmal ion channels using isolated ventricular myocytes under appropriate normoxic and anoxic conditions. Compared with 21 degrees C-acclimated turtles, 5 degrees C-acclimated turtles exhibited a less negative resting membrane potential (by 18-29 mV), a 4.7- to 6.8-fold slower AP upstroke rate, and a 4.2- to 4.9-fold greater AP duration. Correspondingly, peak densities of ventricular voltage-gated Na(+) (I(Na)) and L-type Ca(2+) currents and inward slope conductances of inward rectifier K(+) (I(K1)) channel current were approximately 1/7th (Q(10) = 3.4), 1/13th (Q(10) = 5.0), and one-half (Q(10) = 1.4) of those of 21 degrees C-acclimated ventricular myocytes, respectively. With anoxia at 21 degrees C, peak I(Na) density doubled and ventricular AP duration increased by 47%, a change proportional to the reported approximately 30% reduction of intrinsic heart rate. In contrast, with anoxia at 5 degrees C, ventricular AP characteristics were unaffected; of the ion currents investigated, only the inward conductance via I(K1) changed significantly (reduced by 46%). The present findings indicate that cold temperature, more so than prolonged anoxia, results in substantial modifications of cardiac APs and reduction of ventricular ion current densities. These changes likely prepare cardiac muscle for winter anoxia conditions.
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Affiliation(s)
- Jonathan A W Stecyk
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
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