1
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Sun YX, Hu LS, Dong YW. Surviving hot summer: Roles of phenotypic plasticity of intertidal mobile species considering microhabitat environmental heterogeneity. J Therm Biol 2023; 117:103686. [PMID: 37669600 DOI: 10.1016/j.jtherbio.2023.103686] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 08/12/2023] [Accepted: 08/13/2023] [Indexed: 09/07/2023]
Abstract
For species inhabiting warming and variable thermal environment, coordinated changes in heat tolerance to temperature fluctuations, which largely depend on phenotypic plasticity, are pivotal in buffering high temperatures. Determining the roles of phenotypic plasticity in wild populations and common garden experiments help us understand how organisms survive hot summer and the warming world. We thus monitored the operative temperature of the intertidal limpets Cellana toreuma in both emergent rock and tidal pool microhabitats from June to October 2021, determined the variations of upper thermal limits of short-term acclimated and long-term acclimated limpets from different microhabitats (emergent rock and tidal pool), and further calculated the relationship between the upper thermal limits and acclimation capacity. Our results indicated that living on the emergent rock, limpets encountered more extreme events in summer. For the short-term acclimated samples, limpets on the emergent rock exhibited obvious variations of sublethal thermal limit (i.e., Arrhenius Break Point of cardiac performance, ABT) during summer months, however, this variation of ABT was absent in the limpets in the tidal pool. After the laboratory long-term acclimation, the ABTs and FLTs (Flat Line Temperature of cardiac performance, as an indicator of lethal temperature) of limpets both on the rock and in the tidal pool increased significantly in October, implying the potential existence of selection during the hot summer. Our results further showed that environmental temperature was an important driver of phenotypic plasticity. This study highlighted the changes in the thermal tolerance of intertidal limpets during summer in different microhabitats.
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Affiliation(s)
- Yong-Xu Sun
- Key Laboratory of Mariculture, Ministry of Education, Fisheries College, Ocean University of China, Qingdao, 266003, China
| | - Li-Sha Hu
- Key Laboratory of Mariculture, Ministry of Education, Fisheries College, Ocean University of China, Qingdao, 266003, China.
| | - Yun-Wei Dong
- Key Laboratory of Mariculture, Ministry of Education, Fisheries College, Ocean University of China, Qingdao, 266003, China
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2
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Gilbert MJH, Middleton EK, Kanayok K, Harris LN, Moore JS, Farrell AP, Speers-Roesch B. Rapid cardiac thermal acclimation in wild anadromous Arctic char (Salvelinus alpinus). J Exp Biol 2022; 225:276421. [PMID: 36000268 DOI: 10.1242/jeb.244055] [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: 01/27/2022] [Accepted: 08/15/2022] [Indexed: 11/20/2022]
Abstract
Migratory fishes commonly encounter large and rapid thermal variation, which has the potential to disrupt essential physiological functions. Thus, we acclimated wild, migratory Arctic char to 13°C (∼7°C above a summer average) for an ecologically relevant period (3 days) and measured maximum heart rate (ƒHmax) during acute warming to determine their ability to rapidly improve cardiac function at high temperatures. Arctic char exhibited rapid compensatory cardiac plasticity similar to past observations following prolonged warm acclimation: They reduced ƒHmax over intermediate temperatures (-8%), improved their ability to increase ƒHmax during warming (+10%), and increased (+1.3°C) the temperature at the onset of an arrhythmic heartbeat, a sign of cardiac failure. Consequently, this rapid cardiac plasticity may help migrating fishes like Arctic char mitigate short-term thermal challenges. Furthermore, by using mobile Arctic research infrastructure in a remote field location, the present study illustrates the potential for field-based, experimental physiology in such locations.
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Affiliation(s)
- Matthew J H Gilbert
- Department of Zoology, University of British Columbia, #4200 - 6270, University Blvd, Vancouver, BC, V6T 1Z4, Canada.,Department of Biological Sciences, University of New Brunswick - Saint John, 100 Tucker Park Rd., Saint John, NB, E2L 4L5, Canada
| | - Ella K Middleton
- Department of Biological Sciences, University of New Brunswick - Saint John, 100 Tucker Park Rd., Saint John, NB, E2L 4L5, Canada
| | - Kevin Kanayok
- Ekaluktutiak Hunters & Trappers Organization, Box 1270, Ekaluktutiak, NU, X0B 0C0, Canada
| | - Les N Harris
- Arctic and Aquatic Research Division, Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, MB, R3T 2N6, Canada
| | - Jean-Sébastien Moore
- Institut de Biologie Intégrative et des Systèmes and Département de Biologie, Université Laval, 1030 Avenue de la Médecine, Quebec City, QC, Québec G1V 0A6, Canada
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, #4200 - 6270, University Blvd, Vancouver, BC, V6T 1Z4, Canada.,Faculty of Land and Food Systems, University of British Columbia, 2357 Main Mall, Vancouver, BC, V6T 1Z4, Canada
| | - Ben Speers-Roesch
- Department of Biological Sciences, University of New Brunswick - Saint John, 100 Tucker Park Rd., Saint John, NB, E2L 4L5, Canada
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3
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Badr A, Hassinen M, Vornanen M. Spatial uniformity of action potentials indicates base-to-apex depolarization and repolarization of rainbow trout (Oncorhynchus mykiss) ventricle. J Exp Biol 2022; 225:276292. [PMID: 35950359 DOI: 10.1242/jeb.244466] [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: 04/26/2022] [Accepted: 08/02/2022] [Indexed: 11/20/2022]
Abstract
The spatial pattern of electrical activation is crucial for a full understanding of fish heart function. However, it remains unclear whether there is regional variation in action potential (AP) morphologies and underlying ion currents. Because the direction of depolarization and spatial differences in the durations of ventricular APs set limits to potential patterns of ventricular repolarization, we determined AP morphologies, underlying ion currents, and ion channel expression in 4 different regions (spongy myocardium; and apex, base, and middle of the compact myocardium), and correlated them with in vivo electrocardiogram (ECG) in rainbow trout (Oncorhynchus mykiss). ECG recorded from 3 leads indicated that the depolarization and repolarization of AP propagate from base-to-apex, and the main depolarization axis of the ventricle is between +90° and +120°. AP shape was uniform across the whole ventricle, and little regional differences were found in density of repolarizing K+ currents or depolarizing Ca2+ and Na+ currents and the underlying transcripts of ion channels, providing compelling evidence for the suggested excitation pattern. The spatial uniformity of AP durations and base-to-apex propagation of activation with a relatively slow velocity of propagation indicates no special ventricular conduction pathway in the trout ventricle like the His-Purkinje system of mammalian hearts. The sequence of repolarization is solely determined by activation time without being affected by regional differences in AP duration.
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Affiliation(s)
- Ahmed Badr
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland.,Sohag University, Faculty of Science, Department of Zoology, 82524 Sohag, Egypt
| | - 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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4
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Welzel G, Schuster S. Electric catfish hearts are not intrinsically immune to electric shocks. J Exp Biol 2022; 225:276258. [PMID: 35946177 DOI: 10.1242/jeb.244307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 07/19/2022] [Indexed: 10/15/2022]
Abstract
High voltage electric shocks cause life threatening cardiac injuries such as sudden cardiac standstill or severe myocardial injury. Here, we analysed the physiology of the heart of the strongly electric catfish (Malapterurus beninensis) that stuns prey with high-voltage shocks but is immune to its own, as well as external, high-voltage shocks. Neither a detailed analysis of the electrocardiogram nor the structure of the heart indicated a specialized cardiac conduction system. Using a suitable perfusion system, we discovered that, despite its immunity in vivo, the explanted heart of electric catfish can readily be activated by external electrical currents and is equally sensitive to electric shock-induced arrhythmias as similar-sized goldfish hearts. The surprise thus is that the electric catfish has a vulnerable heart that requires to be protected by highly efficient but presently unknown means.
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Affiliation(s)
- Georg Welzel
- Department of Animal Physiology, University of Bayreuth, Universitätsstrasse 30, 95447 Bayreuth, Germany
| | - Stefan Schuster
- Department of Animal Physiology, University of Bayreuth, Universitätsstrasse 30, 95447 Bayreuth, Germany
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5
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Longhini LS, Zena LA, Polymeropoulos ET, Rocha ACG, da Silva Leandro G, Prado CPA, Bícego KC, Gargaglioni LH. Thermal Acclimation to the Highest Natural Ambient Temperature Compromises Physiological Performance in Tadpoles of a Stream-Breeding Savanna Tree Frog. Front Physiol 2021; 12:726440. [PMID: 34690802 PMCID: PMC8531205 DOI: 10.3389/fphys.2021.726440] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 09/17/2021] [Indexed: 11/13/2022] Open
Abstract
Amphibians may be more vulnerable to climate-driven habitat modification because of their complex life cycle dependence on land and water. Considering the current rate of global warming, it is critical to identify the vulnerability of a species by assessing its potential to acclimate to warming temperatures. In many species, thermal acclimation provides a reversible physiological adjustment in response to temperature changes, conferring resilience in a changing climate. Here, we investigate the effects of temperature acclimation on the physiological performance of tadpoles of a stream-breeding savanna tree frog (Bokermannohyla ibitiguara) in relation to the thermal conditions naturally experienced in their microhabitat (range: 18.8-24.6°C). We quantified performance measures such as routine and maximum metabolic rate at different test (15, 20, 25, 30, and 34°C) and acclimation temperatures (18 and 25°C). We also measured heart rate before and after autonomic blockade with atropine and sotalol at the respective acclimation temperatures. Further, we determined the critical thermal maximum and warming tolerance (critical thermal maximum minus maximum microhabitat temperature), which were not affected by acclimation. Mass-specific routine and mass-specific maximum metabolic rate, as well as heart rate, increased with increasing test temperatures; however, acclimation elevated mass-specific routine metabolic rate while not affecting mass-specific maximum metabolic rate. Heart rate before and after the pharmacological blockade was also unaffected by acclimation. Aerobic scope in animals acclimated to 25°C was substantially reduced, suggesting that physiological performance at the highest temperatures experienced in their natural habitat is compromised. In conclusion, the data suggest that the tadpoles of B. ibitiguara, living in a thermally stable environment, have a limited capacity to physiologically adjust to the highest temperatures found in their micro-habitat, making the species more vulnerable to future climate change.
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Affiliation(s)
- Leonardo S. Longhini
- Departamento de Morfologia e Fisiologia Animal, Universidade Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, Brazil
| | - Lucas A. Zena
- Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil
| | | | - Aline C. G. Rocha
- Departamento de Morfologia e Fisiologia Animal, Universidade Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, Brazil
| | - Gabriela da Silva Leandro
- Departamento de Morfologia e Fisiologia Animal, Universidade Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, Brazil
| | - Cynthia P. A. Prado
- Departamento de Morfologia e Fisiologia Animal, Universidade Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, Brazil
| | - Kênia C. Bícego
- Departamento de Morfologia e Fisiologia Animal, Universidade Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, Brazil
| | - Luciane H. Gargaglioni
- Departamento de Morfologia e Fisiologia Animal, Universidade Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, Brazil
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6
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Filice M, Imbrogno S, Gattuso A, Cerra MC. Hypoxic and Thermal Stress: Many Ways Leading to the NOS/NO System in the Fish Heart. Antioxidants (Basel) 2021; 10:1401. [PMID: 34573033 PMCID: PMC8471457 DOI: 10.3390/antiox10091401] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 08/27/2021] [Accepted: 08/30/2021] [Indexed: 12/22/2022] Open
Abstract
Teleost fish are often regarded with interest for the remarkable ability of several species to tolerate even dramatic stresses, either internal or external, as in the case of fluctuations in O2 availability and temperature regimes. These events are naturally experienced by many fish species under different time scales, but they are now exacerbated by growing environmental changes. This further challenges the intrinsic ability of animals to cope with stress. The heart is crucial for the stress response, since a proper modulation of the cardiac function allows blood perfusion to the whole organism, particularly to respiratory organs and the brain. In cardiac cells, key signalling pathways are activated for maintaining molecular equilibrium, thus improving stress tolerance. In fish, the nitric oxide synthase (NOS)/nitric oxide (NO) system is fundamental for modulating the basal cardiac performance and is involved in the control of many adaptive responses to stress, including those related to variations in O2 and thermal regimes. In this review, we aim to illustrate, by integrating the classic and novel literature, the current knowledge on the NOS/NO system as a crucial component of the cardiac molecular mechanisms that sustain stress tolerance and adaptation, thus providing some species, such as tolerant cyprinids, with a high resistance to stress.
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Affiliation(s)
| | - Sandra Imbrogno
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036 Arcavacata di Rende, Italy; (M.F.); (M.C.C.)
| | - Alfonsina Gattuso
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036 Arcavacata di Rende, Italy; (M.F.); (M.C.C.)
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7
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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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8
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Adrenergic tone benefits cardiac performance and warming tolerance in two teleost fishes that lack a coronary circulation. J Comp Physiol B 2021; 191:701-709. [PMID: 33738526 PMCID: PMC8241749 DOI: 10.1007/s00360-021-01359-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 02/04/2021] [Accepted: 02/22/2021] [Indexed: 01/14/2023]
Abstract
Tolerance to acute environmental warming in fish is partly governed by the functional capacity of the heart to increase systemic oxygen delivery at high temperatures. However, cardiac function typically deteriorates at high temperatures, due to declining heart rate and an impaired capacity to maintain or increase cardiac stroke volume, which in turn has been attributed to a deterioration of the electrical conductivity of cardiac tissues and/or an impaired cardiac oxygen supply. While autonomic regulation of the heart may benefit cardiac function during warming by improving myocardial oxygenation, contractility and conductivity, the role of these processes for determining whole animal thermal tolerance is not clear. This is in part because interpretations of previous pharmacological in vivo experiments in salmonids are ambiguous and were confounded by potential compensatory increases in coronary oxygen delivery to the myocardium. Here, we tested the previously advanced hypothesis that cardiac autonomic control benefits heart function and acute warming tolerance in perch (Perca fluviatilis) and roach (Rutilus rutilus); two species that lack coronary arteries and rely entirely on luminal venous oxygen supplies for cardiac oxygenation. Pharmacological blockade of β-adrenergic tone lowered the upper temperature where heart rate started to decline in both species, marking the onset of cardiac failure, and reduced the critical thermal maximum (CTmax) in perch. Cholinergic (muscarinic) blockade had no effect on these thermal tolerance indices. Our findings are consistent with the hypothesis that adrenergic stimulation improves cardiac performance during acute warming, which, at least in perch, increases acute thermal tolerance.
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9
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Hassinen M, Dzhumaniiazova I, Abramochkin DV, Vornanen M. Ionic basis of atrioventricular conduction: ion channel expression and sarcolemmal ion currents of the atrioventricular canal of the rainbow trout (Oncorhynchus mykiss) heart. J Comp Physiol B 2021; 191:327-346. [PMID: 33575867 PMCID: PMC7895799 DOI: 10.1007/s00360-021-01344-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 12/15/2020] [Accepted: 01/18/2021] [Indexed: 12/17/2022]
Abstract
Atrioventricular (AV) nodal tissue synchronizes activities of atria and ventricles of the vertebrate heart and is also a potential site of cardiac arrhythmia, e.g., under acute heat stress. Since ion channel composition and ion currents of the fish AV canal have not been previously studied, we measured major cation currents and transcript expression of ion channels in rainbow trout (Oncorhynchus mykiss) AV tissue. Both ion current densities and expression of ion channel transcripts indicate that the fish AV canal has a characteristic electrophysiological phenotype that differs from those of sinoatrial tissue, atrium and ventricle. Two types of cardiomyocytes were distinguished electrophysiologically in trout AV nodal tissue: the one (transitional cell) is functionally intermediate between working atrial/ventricular myocytes and the other (AV nodal cell) has a less negative resting membrane potential than atrial and ventricular myocytes and is a more similar to the sinoatrial nodal cells in ion channel composition. The AV nodal cells are characterized by a small or non-existent inward rectifier potassium current (IK1), low density of fast sodium current (INa) and relatively high expression of T-type calcium channels (CACNA3.1). Pacemaker channel (HCN4 and HCN2) transcripts were expressed in the AV nodal tissue but If current was not found in enzymatically isolated nodal myocytes. The electrophysiological properties of the rainbow trout nodal cells are appropriate for a slow rate of action potential conduction (small INa) and a moderate propensity for pacemaking activity (absence of IK1).
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Affiliation(s)
- Minna Hassinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland
| | - Irina Dzhumaniiazova
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia
| | - Denis V Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia.,Laboratory of Cardiac Electrophysiology, National Medical Research Center for Cardiology, Moscow, Russia.,Department of Physiology, Pirogov Russian National Research Medical University, Moscow, Russia
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland.
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10
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Gilbert MJH, Farrell AP. The thermal acclimation potential of maximum heart rate and cardiac heat tolerance in Arctic char (Salvelinus alpinus), a northern cold-water specialist. J Therm Biol 2020; 95:102816. [PMID: 33454044 DOI: 10.1016/j.jtherbio.2020.102816] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 10/30/2020] [Accepted: 12/12/2020] [Indexed: 10/22/2022]
Abstract
Increasing heart rate (ƒH) is a central, if not primary mechanism used by fishes to support their elevated tissue oxygen consumption during acute warming. Thermal acclimation can adjust this acute response to improve cardiac performance and heat tolerance under the prevailing temperatures. We predict that such acclimation will be particularly important in regions undergoing rapid environmental change such as the Arctic. Therefore, we acclimated Arctic char (Salvelinus alpinus), a high latitude, cold-adapted salmonid, to ecologically relevant temperatures (2, 6, 10, 14 and 18 °C) and examined how thermal acclimation influenced their cardiac heat tolerance by measuring the maximum heart rate (ƒHmax) response to acute warming. As expected, acute warming increased ƒHmax in all Arctic char before ƒHmax reached a peak and then became arrhythmic. The peak ƒHmax, and the temperature at which peak ƒHmax (Tpeak) and that at which arrhythmia first occurred (Tarr) all increased progressively (+33%, 49% and 35%, respectively) with acclimation temperature from 2 to 14 °C. When compared at the same test temperature ƒHmax also decreased by as much as 29% with increasing acclimation temperature, indicating significant thermal compensation. The upper temperature at which fish first lost their equilibrium (critical thermal maximum: CTmax) also increased with acclimation temperature, albeit to a lesser extent (+11%). Importantly, Arctic char experienced mortality after several weeks of acclimation at 18 °C and survivors did not have elevated cardiac thermal tolerance. Collectively, these findings suggest that if wild Arctic char have access to suitable temperatures (<18 °C) for a sufficient duration, warm acclimation can potentially mitigate some of the cardiorespiratory impairments previously documented during acute heat exposure.
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Affiliation(s)
- Matthew J H Gilbert
- Department of Zoology, University of British Columbia, #4200 - 6270, University Blvd, Vancouver, BC, V6T 1Z4, Canada.
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, #4200 - 6270, University Blvd, 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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11
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Vornanen M. Feeling the heat: source–sink mismatch as a mechanism underlying the failure of thermal tolerance. J Exp Biol 2020; 223:223/16/jeb225680. [DOI: 10.1242/jeb.225680] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
ABSTRACT
A mechanistic explanation for the tolerance limits of animals at high temperatures is still missing, but one potential target for thermal failure is the electrical signaling off cells and tissues. With this in mind, here I review the effects of high temperature on the electrical excitability of heart, muscle and nerves, and refine a hypothesis regarding high temperature-induced failure of electrical excitation and signal transfer [the temperature-dependent deterioration of electrical excitability (TDEE) hypothesis]. A central tenet of the hypothesis is temperature-dependent mismatch between the depolarizing ion current (i.e. source) of the signaling cell and the repolarizing ion current (i.e. sink) of the receiving cell, which prevents the generation of action potentials (APs) in the latter. A source–sink mismatch can develop in heart, muscles and nerves at high temperatures owing to opposite effects of temperature on source and sink currents. AP propagation is more likely to fail at the sites of structural discontinuities, including electrically coupled cells, synapses and branching points of nerves and muscle, which impose an increased demand of inward current. At these sites, temperature-induced source–sink mismatch can reduce AP frequency, resulting in low-pass filtering or a complete block of signal transmission. In principle, this hypothesis can explain a number of heat-induced effects, including reduced heart rate, reduced synaptic transmission between neurons and reduced impulse transfer from neurons to muscles. The hypothesis is equally valid for ectothermic and endothermic animals, and for both aquatic and terrestrial species. Importantly, the hypothesis is strictly mechanistic and lends itself to experimental falsification.
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Affiliation(s)
- Matti Vornanen
- Department of Environmental and Biological Sciences , University of Eastern Finland, 80101 Joensuu, Finland
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12
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Haverinen J, Vornanen M. Reduced ventricular excitability causes atrioventricular block and depression of heart rate in fish at critically high temperatures. J Exp Biol 2020; 223:jeb225227. [PMID: 32434803 DOI: 10.1242/jeb.225227] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 05/13/2020] [Indexed: 01/08/2023]
Abstract
At critically high temperature, cardiac output in fish collapses as a result of depression of heart rate (bradycardia). However, the cause of bradycardia remains unresolved. To investigate this, rainbow trout (Oncorhynchus mykiss; acclimated at 12°C) were exposed to acute warming while electrocardiograms were recorded. From 12°C to 25.3°C, electrical excitation between different parts of the heart was coordinated, but above 25.3°C, atrial and ventricular beating rates became partly dissociated because of 2:1 atrioventricular (AV) block. With further warming, atrial rate increased to a peak value of 188±22 beats min-1 at 27°C, whereas the ventricle rate peaked at 124±10 beats min-1 at 25.3°C and thereafter dropped to 111±15 beats min-1 at 27°C. In single ventricular myocytes, warming from 12°C to 25°C attenuated electrical excitability as evidenced by increases in rheobase current and the size of critical depolarization required to trigger action potential. Depression of excitability was caused by temperature-induced decrease in input resistance (sarcolemmal K+ leak via the outward IK1 current) of resting myocytes and decrease in inward charge transfer by the Na+ current (INa) of active myocytes. Collectively, these findings show that at critically high temperatures AV block causes ventricular bradycardia owing to the increased excitation threshold of the ventricle, which is due to changes in the passive (resting ion leak) and active (inward charge movement) electrical properties of ventricular myocytes. The sequence of events from the level of ion channels to cardiac function in vivo provides a mechanistic explanation for the depression of cardiac output in fish at critically high temperature.
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Affiliation(s)
- Jaakko Haverinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, 80101 Joensuu, Finland
| | - Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, 80101 Joensuu, Finland
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13
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Monteiro DA, Taylor EW, McKenzie DJ, Rantin FT, Kalinin AL. Interactive effects of mercury exposure and hypoxia on ECG patterns in two Neotropical freshwater fish species: Matrinxã, Brycon amazonicus and traíra, Hoplias malabaricus. ECOTOXICOLOGY (LONDON, ENGLAND) 2020; 29:375-388. [PMID: 32166694 DOI: 10.1007/s10646-020-02186-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/24/2020] [Indexed: 06/10/2023]
Abstract
Hypoxia and mercury contamination often co-occur in tropical freshwater ecosystems, but the interactive effects of these two stressors on fish populations are poorly known. The effects of mercury (Hg) on recorded changes in the detailed form of the electrocardiogram (ECG) during exposure to progressive hypoxia were investigated in two Neotropical freshwater fish species, matrinxã, Brycon amazonicus and traíra, Hoplias malabaricus. Matrinxã were exposed to a sublethal concentration of 0.1 mg L-1 of HgCl2 in water for 96 h. Traíra were exposed to dietary doses of Hg by being fed over a period of 30 days with juvenile matrinxãs previously exposed to HgCl2, resulting in a dose of 0.45 mg of total Hg per fish, each 96 h. Both species showed a bradycardia in progressive hypoxia. Hg exposure impaired cardiac electrical excitability, leading to first-degree atrioventricular block, plus profound extension of the ventricular action potential (AP) plateau. Moreover, there was the development of cardiac arrhythmias and anomalies such as occasional absence of QRS complexes, extra systoles, negative Q-, R- and S-waves (QRS complex), and T wave inversion, especially in hypoxia below O2 partial pressures (PO2) of 5.3 kPa. Sub-chronic dietary Hg exposure induced intense bradycardia in normoxia in traira, plus lengthening of ventricular AP duration coupled with prolonged QRS intervals. This indicates slower ventricular AP conduction during ventricular depolarization. Overall, the data indicate that both acute waterborne and sub-chronic dietary exposure (trophic level transfer), at sublethal concentrations of mercury, cause damage in electrical stability and rhythm of the heartbeat, leading to myocardial dysfunction, which is further intensified during hypoxia. These changes could lead to impaired cardiac output, with consequences for swimming ability, foraging capacity, and hence growth and/or reproductive performance.
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Affiliation(s)
- Diana A Monteiro
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil.
| | - Edwin W Taylor
- School of Biological Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - David J McKenzie
- UMR Marbec, CNRS - IRD - Ifremer - University of Montpellier, Montpellier, France
| | - Francisco T Rantin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
| | - Ana L Kalinin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
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Ekström A, Gräns A, Sandblom E. Can´t beat the heat? Importance of cardiac control and coronary perfusion for heat tolerance in rainbow trout. J Comp Physiol B 2019; 189:10.1007/s00360-019-01243-7. [PMID: 31707423 DOI: 10.1007/s00360-019-01243-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 10/11/2019] [Accepted: 10/24/2019] [Indexed: 12/11/2022]
Abstract
Coronary perfusion and cardiac autonomic regulation may benefit myocardial oxygen delivery and thermal performance of the teleost heart, and thus influence whole animal heat tolerance. Yet, no study has examined how coronary perfusion affects cardiac output during warming in vivo. Moreover, while β-adrenergic stimulation could protect cardiac contractility, and cholinergic decrease in heart rate may enhance myocardial oxygen diffusion at critically high temperatures, previous studies in rainbow trout (Oncorhynchus mykiss) using pharmacological antagonists to block cholinergic and β-adrenergic regulation showed contradictory results with regard to cardiac performance and heat tolerance. This could reflect intra-specific differences in the extent to which altered coronary perfusion buffered potential negative effects of the pharmacological blockade. Here, we first tested how cardiac performance and the critical thermal maximum (CTmax) were affected following a coronary ligation. We then assessed how these performances were influenced by pharmacological cholinergic or β-adrenergic blockade, hypothesising that the effects of the pharmacological treatment would be more pronounced in coronary ligated trout compared to trout with intact coronaries. Coronary blockade reduced CTmax by 1.5 °C, constrained stroke volume and cardiac output across temperatures, led to earlier cardiac failure and was associated with reduced blood oxygen-carrying capacity. Nonetheless, CTmax and the temperatures for cardiac failure were not affected by autonomic blockade. Collectively, our data show that coronary perfusion improves heat tolerance and cardiac performance in trout, while evidence for beneficial effects of altered cardiac autonomic tone during warming remains inconclusive.
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Affiliation(s)
- Andreas Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30, Göteborg, Sweden.
| | - Albin Gräns
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Göteborg, Sweden
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30, Göteborg, Sweden
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15
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Hassinen M, Korajoki H, Abramochkin D, Krivosheya P, Vornanen M. Transcript expression of inward rectifier potassium channels of Kir2 subfamily in Arctic marine and freshwater fish species. J Comp Physiol B 2019; 189:735-749. [PMID: 31679058 DOI: 10.1007/s00360-019-01241-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 08/30/2019] [Accepted: 10/16/2019] [Indexed: 02/08/2023]
Abstract
Inward rectifier K+ (Kir2) channels are critical for electrical excitability of cardiac myocytes. Here, we examine expression of Kir2 channels in the heart of three Gadiformes species, polar cod (Boreogadus saida) and navaga (Eleginus nawaga) of the Arctic Ocean and burbot (Lota lota) of the temperate lakes to find out the role of Kir2 channels in cardiac adaptation to cold. Five boreal freshwater species: brown trout (Salmo trutta fario), arctic char (Salvelinus alpinus), roach (Rutilus rutilus), perch (Perca fluviatilis) and pike (Esox lucius), and zebrafish (Danio rerio), were included for comparison. Transcript expression of genes encoding Kir2.1a, - 2.1b, - 2.2a, - 2.2b and - 2.4 was studied from atrium and ventricle of thermally acclimated or acclimatized fish by quantitative PCR. Kir2 composition in the polar cod was more diverse than in other species in that all Kir2 isoforms were relatively highly expressed. Kir2 composition of navaga and burbot differed from that of the polar cod as well as from those of other species. The relative expression of Kir2.2 transcripts, especially Kir2.2b, was higher in both atrium and ventricle of navaga and burbot (56-89% from the total Kir2 pool) than in other species (0.1-11%). Thermal acclimation induced only small changes in cardiac Kir2 transcript expression in Gadiformes species. However, Kir2.2b transcripts were upregulated in cold-acclimated navaga and burbot hearts. All in all, the cardiac Kir2 composition seems to be dependent on both phylogenetic position and thermal preference of the fish.
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Affiliation(s)
- Minna Hassinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland.
| | - Hanna Korajoki
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland
| | - Denis Abramochkin
- Department of Human and Animal Physiology, Moscow State University, Leninskiye Gory, 1, 12, Moscow, 119991, Russia.,Ural Federal University, Mira 19, Ekaterinburg, 620002, Russia.,Laboratory of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Russia
| | - Pavel Krivosheya
- Russian Federal Research Institute of Fisheries and Oceanography "VNIRO" Polar Branch of VNIRO, Laboratory of pelagic fish, Akademika Knipovicha st., Murmansk, 183038, Russia, Murmansk, Russia
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland
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16
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Gilbert MJH, Rani V, McKenzie SM, Farrell AP. Autonomic cardiac regulation facilitates acute heat tolerance in rainbow trout: in situ and in vivo support. ACTA ACUST UNITED AC 2019; 222:jeb.194365. [PMID: 31015284 DOI: 10.1242/jeb.194365] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 04/10/2019] [Indexed: 12/27/2022]
Abstract
Acute warming in fish increases heart rate (f H) and cardiac output to peak values, after which performance plateaus or declines and arrhythmia may occur. This cardiac response can place a convective limitation on systemic oxygen delivery at high temperatures. To test the hypothesis that autonomic cardiac regulation protects cardiac performance in rainbow trout during acute warming, we investigated adrenergic and cholinergic regulation during the onset and progression of cardiac limitations. We explored the direct effects of adrenergic stimulation by acutely warming an in situ working perfused heart until arrhythmia occurred, cooling the heart to restore rhythmicity and rewarming with increasing adrenergic stimulation. Adrenergic stimulation produced a clear, dose-dependent increase in the temperature and peak f H achieved prior to the onset of arrhythmia. To examine how this adrenergic protection functions in conjunction with cholinergic vagal inhibition in vivo, rainbow trout fitted with ECG electrodes were acutely warmed in a respirometer until they lost equilibrium (CTmax) with and without muscarinic (atropine) and β-adrenergic (sotalol) antagonists. Trout exhibited roughly equal and opposing cholinergic and adrenergic tone on f H that persisted up to critical temperatures. β-Adrenergic blockade significantly lowered peak f H by 14-17%, while muscarinic blockade significantly lowered the temperature for peak f H by 2.0°C. Moreover, muscarinic and β-adrenergic blockers injected individually or together significantly reduced CTmax by up to 3°C, indicating for the first time that cardiac adrenergic stimulation and cholinergic inhibition can enhance acute heat tolerance in rainbow trout at the level of the heart and the whole animal.
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Affiliation(s)
- Matthew J H Gilbert
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4
| | - Varsha Rani
- Faculty of Land and Food Systems, University of British Columbia, 2357 Main Mall, Vancouver, BC, Canada V6T 1Z4
| | - Sean M McKenzie
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4.,Faculty of Land and Food Systems, University of British Columbia, 2357 Main Mall, Vancouver, BC, Canada V6T 1Z4
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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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18
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Prokkola JM, Nikinmaa M. Circadian rhythms and environmental disturbances – underexplored interactions. J Exp Biol 2018; 221:221/16/jeb179267. [DOI: 10.1242/jeb.179267] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
ABSTRACT
Biological rhythms control the life of virtually all organisms, impacting numerous aspects ranging from subcellular processes to behaviour. Many studies have shown that changes in abiotic environmental conditions can disturb or entrain circadian (∼24 h) rhythms. These expected changes are so large that they could impose risks to the long-term viability of populations. Climate change is a major global stressor affecting the fitness of animals, partially because it challenges the adaptive associations between endogenous clocks and temperature – consequently, one can posit that a large-scale natural experiment on the plasticity of rhythm–temperature interactions is underway. Further risks are posed by chemical pollution and the depletion of oxygen levels in aquatic environments. Here, we focused our attention on fish, which are at heightened risk of being affected by human influence and are adapted to diverse environments showing predictable changes in light conditions, oxygen saturation and temperature. The examined literature to date suggests an abundance of mechanisms that can lead to interactions between responses to hypoxia, pollutants or pathogens and regulation of endogenous rhythms, but also reveals gaps in our understanding of the plasticity of endogenous rhythms in fish and in how these interactions may be disturbed by human influence and affect natural populations. Here, we summarize research on the molecular mechanisms behind environment–clock interactions as they relate to oxygen variability, temperature and responses to pollutants, and propose ways to address these interactions more conclusively in future studies.
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Affiliation(s)
- Jenni M. Prokkola
- Department of Biology, University of Turku, FI-20014 Turku, Finland
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Mikko Nikinmaa
- Department of Biology, University of Turku, FI-20014 Turku, Finland
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19
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Badr A, Abu-Amra ES, El-Sayed MF, Vornanen M. Electrical excitability of roach (Rutilus rutilus) ventricular myocytes: effects of extracellular K+, temperature, and pacing frequency. Am J Physiol Regul Integr Comp Physiol 2018; 315:R303-R311. [DOI: 10.1152/ajpregu.00436.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Exercise, capture, and handling stress in fish can elevate extracellular K+ concentration ([K+]o) with potential impact on heart function in a temperature- and frequency-dependent manner. To this end, the effects of [K+]o on the excitability of ventricular myocytes of winter-acclimatized roach ( Rutilus rutilus) (4 ± 0.5°C) were examined at different test temperatures and varying pacing rates. Frequencies corresponding to in vivo heart rates at 4°C (0.37 Hz), 14°C (1.16 Hz), and 24°C (1.96 Hz) had no significant effect on the excitability of ventricular myocytes. Acute increase of temperature from 4 to 14°C did not affect excitability, but a further rise to 24 markedly decreased excitability: stimulus current and critical depolarization needed to elicit an action potential (AP) were ~25 and 14% higher, respectively, at 24°C than at 4°C and 14°C ( P < 0.05). This depression could be due to temperature-related mismatch between inward Na+ and outward K+ currents. In contrast, an increase of [K+]o from 3 to 5.4 or 8 mM at 24°C reduced the stimulus current needed to trigger AP. However, other aspects of excitability were strongly depressed by high [K+]o: maximum rate of AP upstroke and AP duration were drastically (89 and 50%, respectively) reduced at 8 mM [K+]o in comparison with 3 mM ( P < 0.05). As an extreme case, some myocytes completely failed to elicit all-or-none AP at 8 mM [K+]o at 24°C. Also, amplitude and overshoot of AP were reduced by elevation of [K+]o ( P < 0.05). Although high [K+]o antagonizes the negative effects of high temperature on excitation threshold, the precipitous depression of the rate of AP upstroke and complete loss of excitability in some myocytes suggest that the combination of high temperature and high [K+]o will severely impair ventricular excitability in roach.
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Affiliation(s)
- Ahmed Badr
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
- Department of Zoology, Faculty of Science, Sohag University, Sohag, Egypt
| | - El-Sabry Abu-Amra
- Department of Zoology, Faculty of Science, Sohag University, Sohag, Egypt
| | | | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
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20
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Joyce W, Axelsson M, Egginton S, Farrell AP, Crockett EL, O’Brien KM. The effects of thermal acclimation on cardio-respiratory performance in an Antarctic fish ( Notothenia coriiceps). CONSERVATION PHYSIOLOGY 2018; 6:coy069. [PMID: 30568798 PMCID: PMC6291619 DOI: 10.1093/conphys/coy069] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 11/13/2018] [Accepted: 11/26/2018] [Indexed: 05/21/2023]
Abstract
The Southern Ocean has experienced stable, cold temperatures for over 10 million years, yet particular regions are currently undergoing rapid warming. To investigate the impacts of warming on cardiovascular oxygen transport, we compared the cardio-respiratory performance in an Antarctic notothenioid (Notothenia coriiceps) that was maintained at 0 or 5°C for 6.0-9.5 weeks. When compared at the fish's respective acclimation temperature, the oxygen consumption rate and cardiac output were significantly higher in 5°C-acclimated than 0°C-acclimated fish. The 2.7-fold elevation in cardiac output in 5°C-acclimated fish (17.4 vs. 6.5 ml min-1 kg-1) was predominantly due to a doubling of stroke volume, likely in response to increased cardiac preload, as measured by higher central venous pressure (0.15 vs. 0.08 kPa); tachycardia was minor (29.5 vs. 25.2 beats min-1). When fish were acutely warmed, oxygen consumption rate increased by similar amounts in 0°C- and 5°C-acclimated fish at equivalent test temperatures. In both acclimation groups, the increases in oxygen consumption rate during acute heating were supported by increased cardiac output achieved by elevating heart rate, while stroke volume changed relatively little. Cardiac output was similar between both acclimation groups until 12°C when cardiac output became significantly higher in 5°C-acclimated fish, driven largely by their higher stroke volume. Although cardiac arrhythmias developed at a similar temperature (~14.5°C) in both acclimation groups, the hearts of 5°C-acclimated fish continued to pump until significantly higher temperatures (CTmax for cardiac function 17.7 vs. 15.0°C for 0°C-acclimated fish). These results demonstrate that N. coriiceps is capable of increasing routine cardiac output during both acute and chronic warming, although the mechanisms are different (heart rate-dependent versus primarily stroke volume-dependent regulation, respectively). Cardiac performance was enhanced at higher temperatures following 5°C acclimation, suggesting cardiovascular function may not constrain the capacity of N. coriiceps to withstand a warming climate.
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Affiliation(s)
- William Joyce
- Department of Zoophysiology, Aarhus University, Aarhus C, Denmark
- Corresponding author: Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark.
| | - Michael Axelsson
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Stuart Egginton
- School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | | | - Kristin M O’Brien
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA
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Badr A, Korajoki H, Abu-Amra ES, El-Sayed MF, Vornanen M. Effects of seasonal acclimatization on thermal tolerance of inward currents in roach (Rutilus rutilus) cardiac myocytes. J Comp Physiol B 2017; 188:255-269. [DOI: 10.1007/s00360-017-1126-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 08/23/2017] [Accepted: 09/15/2017] [Indexed: 02/06/2023]
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22
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Hassinen M, Haverinen J, Vornanen M. Small functional If current in sinoatrial pacemaker cells of the brown trout ( Salmo trutta fario) heart despite strong expression of HCN channel transcripts. Am J Physiol Regul Integr Comp Physiol 2017; 313:R711-R722. [PMID: 28855177 DOI: 10.1152/ajpregu.00227.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 08/21/2017] [Accepted: 08/24/2017] [Indexed: 01/26/2023]
Abstract
Funny current (If), formed by hyperpolarization-activated cyclic nucleotide-gated channels (HCN channels), is supposed to be crucial for the membrane clock regulating the cardiac pacemaker mechanism. We examined the presence and activity of HCN channels in the brown trout (Salmo trutta fario) sinoatrial (SA) pacemaker cells and their putative role in heart rate (fH) regulation. Six HCN transcripts (HCN1, HCN2a, HCN2ba, HCN2bb, HCN3, and HCN4) were expressed in the brown trout heart. The total HCN transcript abundance was 4.0 and 4.9 times higher in SA pacemaker tissue than in atrium and ventricle, respectively. In the SA pacemaker, HCN3 and HCN4 were the main isoforms representing 35.8 ± 2.7 and 25.0 ± 1.5%, respectively, of the total HCN transcripts. Only a small If with a mean current density of -1.2 ± 0.37 pA/pF at -140 mV was found in 4 pacemaker cells out of 16 spontaneously beating cells examined, despite the optimization of recording conditions for If activity. If was not found in any of the 24 atrial myocytes and 21 ventricular myocytes examined. HCN4 coexpressed with the MinK-related peptide 1 (MiRP1) β-subunit in CHO cells generated large If currents. In contrast, HCN3 (+MiRP1) failed to produce If in the same expression system. Cs+ (2 mM), which blocked 84 ± 12% of the native If, reversibly reduced fH 19.2 ± 3.6% of the excised multicellular pacemaker tissue from 53 ± 5 to 44 ± 5 beats/min (P < 0.05). However, this effect was probably due to the reduction of IKr, which was also inhibited (63.5 ± 4.6%) by Cs+ These results strongly suggest that fH regulation in the brown trout heart is largely independent on If.
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Affiliation(s)
- Minna Hassinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Jaakko Haverinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
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23
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Badr A, Hassinen M, El-Sayed MF, Vornanen M. Effects of seasonal acclimatization on action potentials and sarcolemmal K+ currents in roach (Rutilus rutilus) cardiac myocytes. Comp Biochem Physiol A Mol Integr Physiol 2017; 205:15-27. [DOI: 10.1016/j.cbpa.2016.12.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 12/13/2016] [Accepted: 12/15/2016] [Indexed: 01/10/2023]
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24
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Haverinen J, Abramochkin DV, Kamkin A, Vornanen M. Maximum heart rate in brown trout (Salmo trutta fario) is not limited by firing rate of pacemaker cells. Am J Physiol Regul Integr Comp Physiol 2017; 312:R165-R171. [DOI: 10.1152/ajpregu.00403.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 11/23/2016] [Accepted: 11/23/2016] [Indexed: 01/17/2023]
Abstract
Temperature-induced changes in cardiac output (Q̇) in fish are largely dependent on thermal modulation of heart rate ( fH), and at high temperatures Q̇ collapses due to heat-dependent depression of fH. This study tests the hypothesis that firing rate of sinoatrial pacemaker cells sets the upper thermal limit of fH in vivo. To this end, temperature dependence of action potential (AP) frequency of enzymatically isolated pacemaker cells (pacemaker rate, fPM), spontaneous beating rate of isolated sinoatrial preparations ( fSA), and in vivo fH of the cold-acclimated (4°C) brown trout ( Salmo trutta fario) were compared under acute thermal challenges. With rising temperature, fPM steadily increased because of the acceleration of diastolic depolarization and shortening of AP duration up to the break point temperature (TBP) of 24.0 ± 0.37°C, at which point the electrical activity abruptly ceased. The maximum fPM at TBP was much higher [193 ± 21.0 beats per minute (bpm)] than the peak fSA (94.3 ± 6.0 bpm at 24.1°C) or peak fH (76.7 ± 2.4 at 15.7 ± 0.82°C) ( P < 0.05). These findings strongly suggest that the frequency generator of the sinoatrial pacemaker cells does not limit fH at high temperatures in the brown trout in vivo.
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Affiliation(s)
- Jaakko Haverinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Denis V. Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory, Moscow, Russia; and
- Department of Physiology, Pirogov Russian National Research Medical University, Ostrovityanova, Moscow, Russia
| | - Andre Kamkin
- Department of Physiology, Pirogov Russian National Research Medical University, Ostrovityanova, Moscow, Russia
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
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25
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26
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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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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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Abramochkin DV, Vornanen M. Seasonal changes of cholinergic response in the atrium of Arctic navaga cod (Eleginus navaga). J Comp Physiol B 2016; 187:329-338. [PMID: 27672043 DOI: 10.1007/s00360-016-1032-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Revised: 08/26/2016] [Accepted: 09/13/2016] [Indexed: 11/24/2022]
Abstract
Fishes of north-temperate latitudes exhibit marked seasonal changes in electrical excitability of the heart partly as an outcome of temperature-dependent changes in the density of major K+ ion currents: delayed rectifiers (IKr, IKs) and background inward rectifier (IK1). In the arctic teleost, navaga cod (Eleginus navaga), IKr and IK1 are strongly up-regulated in winter. The current study tests the hypothesis that the ligand-gated K+ current, the acetylcholine-activated inward rectifier, IKACh, is also modified by seasonal acclimatization in atrial myocytes of navaga. In sinoatrial preparations of the summer-acclimatized (SA) navaga, 10-6 M carbamylcholine chloride (CCh) caused slowing of heart rate, shortening of atrial action potential (AP) duration and a drastic reduction of AP amplitude, eventually resulting in inexcitability. In winter-acclimatized (WA) atria CCh slowed HR and reduced AP duration, but reduction of AP amplitude was modest and never resulted in inexcitability. The difference in cholinergic response between SA and WA navaga is explained by seasonal changes in IKACh density. The peak density of IKACh, induced by 10-5 M CCh, at the common experimental temperature (+6 °C) was 0.97 ± 0.28 pA/pF in SA navaga but only 0.183 ± 0.013 pA/pF in WA navaga (a 5.3-fold difference, P < 0.05). At acclimatization temperatures of the fish IKACh density was 2.8 ± 0.50 (at +12 °C) and 0.11 ± 0.06 pA/pF (at +3 °C) (a 26-fold difference, P < 0.05) for SA and WA navaga, respectively. Thus, acclimatization to summer induces a drastic up-regulation of the atrial IKACh, which effectively shortens atrial AP. The reverse temperature compensation of the atrial IKACh may be advantageous in summer under variable water temperatures and oxygen concentrations by reducing workload of the heart.
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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.
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
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Drost HE, Lo M, Carmack EC, Farrell AP. Acclimation potential of Arctic cod (Boreogadus saida) from the rapidly warming Arctic Ocean. ACTA ACUST UNITED AC 2016; 219:3114-3125. [PMID: 27471275 DOI: 10.1242/jeb.140194] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 07/25/2016] [Indexed: 01/07/2023]
Abstract
As a consequence of the growing concern about warming of the Arctic Ocean, this study quantified the thermal acclimation responses of Boreogadus saida, a key Arctic food web fish. Physiological rates for cardio-respiratory functions as well as critical maximum temperature (Tc,max) for loss of equilibrium (LOE) were measured. The transition temperatures for these events (LOE, the rate of oxygen uptake and maximum heart rate) during acute warming were used to gauge phenotypic plasticity after thermal acclimation from 0.5°C up to 6.5°C for 1 month (respiratory and Tc,max measurements) and 6 months (cardiac measurements). Tc,max increased significantly by 2.3°C from 14.9°C to 17.1°C with thermal acclimation, while the optimum temperature for absolute aerobic scope increased by 4.5°C over the same range of thermal acclimation. Warm acclimation reset the maximum heart rate to a statistically lower rate, but the first Arrhenius breakpoint temperature during acute warming was unchanged. The hierarchy of transition temperatures was quantified at three acclimation temperatures and was fitted inside a Fry temperature tolerance polygon to better define ecologically relevant thermal limits to performance of B. saida We conclude that B. saida can acclimate to 6.5°C water temperatures in the laboratory. However, at this acclimation temperature 50% of the fish were unable to recover from maximum swimming at the 8.5°C test temperature and their cardio-respiratory performance started to decline at water temperatures greater than 5.4°C. Such costs in performance may limit the ecological significance of B. saida acclimation potential.
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Affiliation(s)
- H E Drost
- Zoology Department, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4
| | - M Lo
- Zoology Department, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4
| | - E C Carmack
- Institute of Ocean Sciences, Fisheries and Oceans Canada, 9860 West Saanich Road, Sidney, British Columbia, Canada V8L 4B2
| | - A P Farrell
- Zoology Department, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4 Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
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31
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Vornanen M. The temperature dependence of electrical excitability in fish hearts. J Exp Biol 2016; 219:1941-52. [DOI: 10.1242/jeb.128439] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 05/17/2016] [Indexed: 01/08/2023]
Abstract
ABSTRACT
Environmental temperature has pervasive effects on the rate of life processes in ectothermic animals. Animal performance is affected by temperature, but there are finite thermal limits for vital body functions, including contraction of the heart. This Review discusses the electrical excitation that initiates and controls the rate and rhythm of fish cardiac contraction and is therefore a central factor in the temperature-dependent modulation of fish cardiac function. The control of cardiac electrical excitability should be sensitive enough to respond to temperature changes but simultaneously robust enough to protect against cardiac arrhythmia; therefore, the thermal resilience and plasticity of electrical excitation are physiological qualities that may affect the ability of fishes to adjust to climate change. Acute changes in temperature alter the frequency of the heartbeat and the duration of atrial and ventricular action potentials (APs). Prolonged exposure to new thermal conditions induces compensatory changes in ion channel expression and function, which usually partially alleviate the direct effects of temperature on cardiac APs and heart rate. The most heat-sensitive molecular components contributing to the electrical excitation of the fish heart seem to be Na+ channels, which may set the upper thermal limit for the cardiac excitability by compromising the initiation of the cardiac AP at high temperatures. In cardiac and other excitable cells, the different temperature dependencies of the outward K+ current and inward Na+ current may compromise electrical excitability at temperature extremes, a hypothesis termed the temperature-dependent depression of electrical excitation.
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Affiliation(s)
- Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, PO Box 111, Joensuu 80101, Finland
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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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