1
|
Schwieterman GD, Hardison EA, Cox GK, Van Wert JC, Birnie-Gauvin K, Eliason EJ. Mechanisms of cardiac collapse at high temperature in a marine teleost (Girella nigrians). Comp Biochem Physiol A Mol Integr Physiol 2023; 286:111512. [PMID: 37726058 DOI: 10.1016/j.cbpa.2023.111512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/11/2023] [Accepted: 09/11/2023] [Indexed: 09/21/2023]
Abstract
Heat-induced mortality in ectotherms may be attributed to impaired cardiac performance, specifically a collapse in maximum heart rate (fHmax), although the physiological mechanisms driving this phenomenon are still unknown. Here, we tested two proposed factors which may restrict cardiac upper thermal limits: noxious venous blood conditions and oxygen limitation. We hypothesized elevated blood [K+] (hyperkalemia) and low oxygen (hypoxia) would reduce cardiac upper thermal limits in a marine teleost (Girella nigricans), while high oxygen (hyperoxia) would increase thermal limits. We also hypothesized higher acclimation temperatures would exacerbate the harmful effects of an oxygen limitation. Using the Arrhenius breakpoint temperature test, we measured fHmax in acutely warmed fish under control (saline injected) and hyperkalemic conditions (elevated plasma [K+]) while exposed to hyperoxia (200% air saturation), normoxia (100% air saturation), or hypoxia (20% air saturation). We also measured ventricle lactate content and venous blood oxygen partial pressure (PO2) to determine if there were universal thresholds in either metric driving cardiac collapse. Elevated [K+] was not significantly correlated with any cardiac thermal tolerance metric. Hypoxia significantly reduced cardiac upper thermal limits (Arrhenius breakpoint temperature [TAB], peak fHmax, temperature of peak heart rate [TPeak], and temperature at arrhythmia [TARR]). Hyperoxia did not alter cardiac thermal limits compared to normoxia. There was no evidence of a species-wide threshold in ventricular [lactate] or venous PO2. Here, we demonstrate that oxygen limits cardiac thermal tolerance only in instances of hypoxia, but that other physiological processes are responsible for causing temperature-induced heart failure when oxygen is not limited.
Collapse
Affiliation(s)
- Gail D Schwieterman
- Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA; School of Marine Sciences, University of Maine, Orono, ME, USA; Maine Agricultural and Forest Experiment Station, Orono, ME, USA.
| | - Emily A Hardison
- Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA. https://twitter.com/eahardison
| | | | - Jacey C Van Wert
- Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA. https://twitter.com/jacey_van_wert
| | - Kim Birnie-Gauvin
- Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA; Section for Freshwater Fisheries and Ecology, National Institute of Aquatic Resources, Technical University of Denmark, Silkeborg, Denmark. https://twitter.com/kbg_conserv
| | - Erika J Eliason
- Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA
| |
Collapse
|
2
|
Joyce W, Warwicker J, Shiels HA, Perry SF. Evolution and divergence of teleost adrenergic receptors: why sometimes 'the drugs don't work' in fish. J Exp Biol 2023; 226:jeb245859. [PMID: 37823524 DOI: 10.1242/jeb.245859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
Adrenaline and noradrenaline, released as hormones and/or neurotransmitters, exert diverse physiological functions in vertebrates, and teleost fishes are widely used as model organisms to study adrenergic regulation; however, such investigations often rely on receptor subtype-specific pharmacological agents (agonists and antagonists; see Glossary) developed and validated in mammals. Meanwhile, evolutionary (phylogenetic and comparative genomic) studies have begun to unravel the diversification of adrenergic receptors (ARs) and reveal that whole-genome duplications and pseudogenization events in fishes results in notable distinctions from mammals in their genomic repertoire of ARs, while lineage-specific gene losses within teleosts have generated significant interspecific variability. In this Review, we visit the evolutionary history of ARs (including α1-, α2- and β-ARs) to highlight the prominent interspecific differences in teleosts, as well as between teleosts and other vertebrates. We also show that structural modelling of teleost ARs predicts differences in ligand binding affinity compared with mammalian orthologs. To emphasize the difficulty of studying the roles of different AR subtypes in fish, we collate examples from the literature of fish ARs behaving atypically compared with standard mammalian pharmacology. Thereafter, we focus on specific case studies of the liver, heart and red blood cells, where our understanding of AR expression has benefited from combining pharmacological approaches with molecular genetics. Finally, we briefly discuss the ongoing advances in 'omics' technologies that, alongside classical pharmacology, will provide abundant opportunities to further explore adrenergic signalling in teleosts.
Collapse
Affiliation(s)
- William Joyce
- Department of Biology - Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
| | - Jim Warwicker
- Division of Molecular and Cellular Function, Faculty of Biology, Medicine and Health, Manchester Institute of Biotechnology, The University of Manchester, Manchester, M1 7DN, UK
| | - Holly A Shiels
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PL, UK
| | - Steve F Perry
- Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON, Canada, K1N 6N5
| |
Collapse
|
3
|
Van Wert JC, Hendriks B, Ekström A, Patterson DA, Cooke SJ, Hinch SG, Eliason EJ. Population variability in thermal performance of pre-spawning adult Chinook salmon. CONSERVATION PHYSIOLOGY 2023; 11:coad022. [PMID: 37152448 PMCID: PMC10157787 DOI: 10.1093/conphys/coad022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 02/22/2023] [Accepted: 04/03/2023] [Indexed: 05/09/2023]
Abstract
Climate change is causing large declines in many Pacific salmon populations. In particular, warm rivers are associated with high levels of premature mortality in migrating adults. The Fraser River watershed in British Columbia, Canada, supports some of the largest Chinook salmon (Oncorhynchus tshawytscha) runs in the world. However, the Fraser River is warming at a rate that threatens these populations at critical freshwater life stages. A growing body of literature suggests salmonids are locally adapted to their thermal migratory experience, and thus, population-specific thermal performance information can aid in management decisions. We compared the thermal performance of pre-spawning adult Chinook salmon from two populations, a coastal fall-run from the Chilliwack River (125 km cooler migration) and an interior summer-run from the Shuswap River (565 km warmer migration). We acutely exposed fish to temperatures reflecting current (12°C, 18°C) and future projected temperatures (21°C, 24°C) in the Fraser River and assessed survival, aerobic capacity (resting and maximum metabolic rates, absolute aerobic scope (AAS), muscle and ventricle citrate synthase), anaerobic capacity (muscle and ventricle lactate dehydrogenase) and recovery capacity (post-exercise metabolism, blood physiology, tissue lactate). Chilliwack Chinook salmon performed worse at high temperatures, indicated by elevated mortality, reduced breadth in AAS, enhanced plasma lactate and potassium levels and elevated tissue lactate concentrations compared with Shuswap Chinook salmon. At water temperatures exceeding the upper pejus temperatures (Tpejus, defined here as 80% of maximum AAS) of Chilliwack (18.7°C) and Shuswap (20.2°C) Chinook salmon populations, physiological performance will decline and affect migration and survival to spawn. Our results reveal population differences in pre-spawning Chinook salmon performance across scales of biological organization at ecologically relevant temperatures. Given the rapid warming of rivers, we show that it is critical to consider the intra-specific variation in thermal physiology to assist in the conservation and management of Pacific salmon.
Collapse
Affiliation(s)
- Jacey C Van Wert
- Corresponding author: Department of Ecology, Evolution & Marine Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9620, USA.
| | - Brian Hendriks
- Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Andreas Ekström
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
- Department of Biological and Environmental Sciences, University of Gothenburg, 41390 Gothenburg, Sweden
| | - David A Patterson
- Fisheries and Oceans Canada, Science Branch, Cooperative Resource Management Institute, School of Resource and Environmental Management, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Steven J Cooke
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Scott G Hinch
- Pacific Salmon Ecology and Conservation Laboratory, Department of Forest and Conservation Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Erika J Eliason
- Department of Ecology, Evolution & Marine Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9620, USA
| |
Collapse
|
4
|
Mortensen HS, Jacobsen E, Kolarevic J, Vang A. Exposing Atlantic Salmon Post-Smolts to Fluctuating Sublethal Nitrite Concentrations in a Commercial Recirculating Aquaculture System (RAS) May Have Negative Consequences. FRONTIERS IN ANIMAL SCIENCE 2022. [DOI: 10.3389/fanim.2022.886071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Salmon farmers are interested in extending the time post-smolts are reared in recirculating aquaculture systems (RAS). However, there is a lack of knowledge regarding optimal water quality for post-smolts in RAS, and regarding potential consequences of long term exposure to different toxic compounds, such as nitrite, in the RAS water. To address this issue, we conducted a case study at a Faroese Atlantic salmon farm, that rears large post-smolts in fresh water RAS for 22 months before sea transfer, with no additional chloride salt, a known treatment for nitrite toxicity. The aim was to document the potential effects of long-term exposure of fluctuating sub-lethal nitrite concentrations in fresh water RAS on blood physiology of large post-smolts. The study was conducted over six weeks, at the end of the RAS production cycle. Our case study shows that after ~22 months in RAS with no additional chloride, the fish had accumulated a plasma nitrite concentration 8 to 16 times higher than the ambient water. Our results indicate that the accumulation may have resulted in extracellular hyperkaliemia, since there was a positive correlation between plasma nitrite and potassium levels (p=0.00095), with potassium levels almost twice as high than previously reported for Atlantic salmon. This could indicate that Atlantic salmon health is challenged due to prolonged sub-lethal nitrite exposure in fresh water RAS. Further research related to long-term nitrite exposure in RAS is needed to asses the potential negative impact, in order to optimize welfare and growth performance during production of Atlantic salmon post-smolts.
Collapse
|
5
|
Sandra I, Verri T, Filice M, Barca A, Schiavone R, Gattuso A, Cerra MC. Shaping the cardiac response to hypoxia: NO and its partners in teleost fish. Curr Res Physiol 2022; 5:193-202. [PMID: 35434651 PMCID: PMC9010694 DOI: 10.1016/j.crphys.2022.03.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 03/14/2022] [Accepted: 03/31/2022] [Indexed: 12/12/2022] Open
Abstract
The reduced availability of dissolved oxygen is a common stressor in aquatic habitats that affects the ability of the heart to ensure tissue oxygen supply. Among key signalling molecules activated during cardiac hypoxic stress, nitric oxide (NO) has emerged as a central player involved in the related adaptive responses. Here, we outline the role of the nitrergic control in modulating tolerance and adaptation of teleost heart to hypoxia, as well as major molecular players that participate in the complex NO network. The purpose is to provide a framework in which to depict how the heart deals with limitations in oxygen supply. In this perspective, defining the relational interplay between the multiple (sets of) proteins that, due to the gene duplication events that occurred during the teleost fish evolutive radiation, do operate in parallel with similar functions in the (different) heart (districts) and other body districts under low levels of oxygen supply, represents a next goal of the comparative research in teleost fish cardiac physiology. The flexibility of the teleost heart to O2 limitations is illustrated by using cyprinids as hypoxia tolerance models. Major molecular mediators of the teleost cardiac response are discussed with a focus on the nitrergic system. A comparative analysis of gene duplication highlights conserved targets which may orchestrate the cardiac response to hypoxia.
Collapse
|
6
|
Rasmussen M, Feng HZ, Jin JP. Evolution of the N-Terminal Regulation of Cardiac Troponin I for Heart Function of Tetrapods: Lungfish Presents an Example of the Emergence of Novel Submolecular Structure to Lead the Capacity of Adaptation. J Mol Evol 2022; 90:30-43. [PMID: 34966949 PMCID: PMC10926322 DOI: 10.1007/s00239-021-10039-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 11/27/2021] [Indexed: 11/26/2022]
Abstract
Troponin-based Ca2+ regulation of striated muscle contraction emerged approximately 700 million years ago with largely conserved functions during evolution. Troponin I (TnI) is the inhibitory subunit of troponin and has evolved into three muscle type-specific isoforms in vertebrates. Cardiac TnI is specifically expressed in the adult heart and has a unique N-terminal extension implicating a specific value during natural selection. The N-terminal extension of cardiac TnI in higher vertebrates contains β-adrenergic-regulated protein kinase A (PKA) phosphorylation sites as a mechanism to enhance cardiac muscle relaxation and facilitate ventricular filling. Phylogenic studies showed that the N-terminal extension of cardiac TnI first emerged in the genomes of early tetrapods as well as primordial lobe-finned fishes such as the coelacanth whereas it is absent in ray-finned fish. This apparently rapid evolution of β-adrenergic regulation of cardiac function suggests a high selection value for the heart of vertebrate animals on land to work under higher metabolic demands. Sequencing and PKA phosphorylation data showed that lungfish cardiac TnI has evolved with an amphibian-like N-terminal extension with prototype PKA phosphorylation sites while its overall structure remained fish like. The data demonstrate that the submolecular structure of TnI may evolve ahead of the whole protein for cardiac muscle contractility to adapt to new environmental conditions. Understanding the evolution of the β-adrenergic regulation of TnI and cardiac adaptation to the increased energetic demands of life on land adds knowledge for the treatment of human heart diseases and failure.
Collapse
Affiliation(s)
- Monica Rasmussen
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, 48201, USA
| | - Han-Zhong Feng
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, 60612, USA
| | - J-P Jin
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, 48201, USA.
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, 60612, USA.
| |
Collapse
|
7
|
Morgenroth D, McArley T, Gräns A, Axelsson M, Sandblom E, Ekström A. Coronary blood flow influences tolerance to environmental extremes in fish. J Exp Biol 2021; 224:jeb.239970. [PMID: 33688058 DOI: 10.1242/jeb.239970] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 03/03/2021] [Indexed: 12/16/2022]
Abstract
Approximately half of all fishes have, in addition to the luminal venous O2 supply, a coronary circulation supplying the heart with fully oxygenated blood. Yet, it is not fully understood how coronary O2 delivery affects tolerance to environmental extremes such as warming and hypoxia. Hypoxia reduces arterial oxygenation, while warming increases overall tissue O2 demand. Thus, as both stressors are associated with reduced venous O2 supply to the heart, we hypothesised that coronary flow benefits hypoxia and warming tolerance. To test this hypothesis, we blocked coronary blood flow (via surgical coronary ligation) in rainbow trout (Oncorhynchus mykiss) and assessed how in vivo cardiorespiratory performance and whole-animal tolerance to acute hypoxia and warming was affected. While coronary ligation reduced routine stroke volume relative to trout with intact coronaries, cardiac output was maintained by an increase in heart rate. However, in hypoxia, coronary-ligated trout were unable to increase stroke volume to maintain cardiac output when bradycardia developed, which was associated with a slightly reduced hypoxia tolerance. Moreover, during acute warming, coronary ligation caused cardiac function to collapse at lower temperatures and reduced overall heat tolerance relative to trout with intact coronary arteries. We also found a positive relationship between individual hypoxia and heat tolerance across treatment groups, and tolerance to both environmental stressors was positively correlated with cardiac performance. Collectively, our findings show that coronary perfusion improves cardiac O2 supply and therefore cardiovascular function at environmental extremes, which benefits tolerance to natural and anthropogenically induced environmental perturbations.
Collapse
Affiliation(s)
- Daniel Morgenroth
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| | - Tristan McArley
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| | - Albin Gräns
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, 532 23 Skara, Sweden
| | - Michael Axelsson
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| | - Andreas Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| |
Collapse
|
8
|
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.
Collapse
|
9
|
The effects of elevated potassium, acidosis, reduced oxygen levels, and temperature on the functional properties of isolated myocardium from three elasmobranch fishes: clearnose skate (Rostroraja eglanteria), smooth dogfish (Mustelus canis), and sandbar shark (Carcharhinus plumbeus). J Comp Physiol B 2021; 191:127-141. [PMID: 33394123 DOI: 10.1007/s00360-020-01328-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 10/27/2020] [Accepted: 11/15/2020] [Indexed: 10/22/2022]
Abstract
Elevated plasma potassium levels (hyperkalemia), reduced plasma pH (acidosis), reduced blood oxygen content, and elevated temperatures are associated with species-specific rates of at-vessel and post-release mortality in elasmobranch fishes. The mechanism linking these physiological disturbances to mortality remains undetermined however, and we hypothesize that the proximate cause is reduced myocardial function. We measured changes in the functional properties of isolated ventricular myocardial strips from clearnose skate (Rostroraja eglanteria), smooth dogfish (Mustelus canis), and sandbar shark (Carcharhinus plumbeus) when subjected to the following stressors (both in isolation and in combination): hyperkalemia (7.4 mM K+), acidosis (from 7.9 to 7.1), and reduced oxygen (to 31% O2 saturation) applied at temperatures 5 °C above and below holding temperatures. We selected these species based on phylogenetic distance, diverse routine activity levels, and their tolerance to capture and transport. Stressors had a few significant species-specific detrimental impacts on myocardial function (e.g., a 33-45% decrease in net force under acidosis + low O2). Net force production of myocardial strips from clearnose skate and smooth dogfish approximately doubled following exposure to isoproterenol, demonstrating that these species possess beta-adrenergic receptors and that their stimulation could provide a mechanism for preservation of cardiac function during stress. Our results suggest that disruption of physiological homeostasis associated with capture may fatally impair cardiac function in some elasmobranch species, although research with more severe stressors is needed.
Collapse
|
10
|
Roberts JC, Carnevale C, Gamperl AK, Syme DA. Effects of hypoxic acclimation on contractile properties of the spongy and compact ventricular myocardium of steelhead trout (Oncorhynchus mykiss). J Comp Physiol B 2020; 191:99-111. [PMID: 33084921 DOI: 10.1007/s00360-020-01318-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 09/10/2020] [Accepted: 09/29/2020] [Indexed: 11/28/2022]
Abstract
The trout ventricle has an outer compact layer supplied with well-oxygenated arterial blood from the coronary circulation, and an inner spongy myocardium supplied with oxygen poor venous blood. It was hypothesized that: (1) the spongy myocardium of steelhead trout (Oncorhynchus mykiss), given its routine exposure to low partial pressures of oxygen (PO2), would be better able to maintain contractile performance (work) when exposed to acute hypoxia (100 to 10% air saturation) relative to the compact myocardium, and would show little benefit from hypoxic acclimation; and (2) the compact myocardium from hypoxia-acclimated (40% air saturation) fish would be better able to maintain work during acute exposure to hypoxia relative to normoxia-acclimated individuals. Consistent with our expectations, when PO2 was acutely lowered, net work from the compact myocardium of normoxia-acclimated fish declined more (by ~ 73%) than the spongy myocardium (~ 50%), and more than the compact myocardium of hypoxia-acclimated fish (~ 55%), and hypoxic acclimation did not benefit the spongy myocardium in the face of reduced PO2. Further, while hypoxic acclimation resulted in a 25% (but not significant) decrease in net work of the spongy myocardium, the performance of the compact myocardium almost doubled. This research suggests that, in contrast to the spongy myocardium, performance of the compact myocardium is improved by hypoxic acclimation; and supports previous research suggesting that the decreased contractile performance of the myocardium upon exposure to lowered PO2 may be adaptive and mediated by mechanisms within the muscle itself.
Collapse
Affiliation(s)
- Jordan C Roberts
- Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
| | - Christian Carnevale
- Departments of Ocean Sciences and Biology, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada
| | - A Kurt Gamperl
- Departments of Ocean Sciences and Biology, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada
| | - Douglas A Syme
- Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada.
| |
Collapse
|
11
|
Goulding AT, Farrell AP. The effect of temperature acclimation on the force-frequency relationship and adrenergic sensitivity of the ventricle of two populations of juvenile sockeye salmon. J Comp Physiol B 2020; 190:717-730. [PMID: 32770260 DOI: 10.1007/s00360-020-01299-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 06/08/2020] [Accepted: 07/15/2020] [Indexed: 11/26/2022]
Abstract
We tested the hypothesis that cardiorespiratory differences known to exist among adult sockeye salmon populations also exist in the juveniles. To test this hypothesis, we compared cardiac contractility and adrenergic responsiveness of juvenile sockeye salmon from two geographically isolated populations that were reared from eggs under common garden conditions and at two acclimation temperatures (5 °C and 14 °C). However, we found no substantive differences in the force-frequency response (FFR) and the cardiac pumping capacity of juveniles from Weaver Creek and Chilko River populations, even when we considered wild-reared juveniles from one of the populations. An unexpected discovery for all fish groups at 5 °C was a rather flat FFR during tonic β-adrenergic stimulation (βAR) stimulation. Curiously, while active tension nearly doubled with maximum βAR stimulation at low pacing frequencies for all fish groups, a negative FFR with maximum βAR stimulation meant that this inotropic benefit was lost at the highest pacing frequency (0.8 Hz). Active tension with tonic βAR stimulation was similar at 14 °C, but maximum pacing frequency doubled and all fish groups displayed a modest negative FFR. Maximum βAR stimulation again doubled active tension and this benefit was retained even at the highest pacing frequency (1.6 Hz) at 14 °C. Even though subtle population differences were apparent for the FFR and pumping capacity, their biological significance is unclear. What is clear, however, is that the cardiac pumping capacity of juvenile sockeye would benefit more from βAR stimulation swimming at 15 °C than when swimming at 5 °C.
Collapse
Affiliation(s)
- A T Goulding
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada.
| | - A P Farrell
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada
- Faculty of Land and Food Systems, University of British Columbia, 2357 Main Mall, Vancouver, BC, V6T 1Z4, Canada
| |
Collapse
|
12
|
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.
Collapse
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
| |
Collapse
|
13
|
Leo S, Gattuso A, Mazza R, Filice M, Cerra MC, Imbrogno S. Cardiac influence of the β3-adrenoceptor in the goldfish ( Carassius auratus): a protective role under hypoxia? ACTA ACUST UNITED AC 2019; 222:jeb.211334. [PMID: 31527180 DOI: 10.1242/jeb.211334] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 09/11/2019] [Indexed: 12/18/2022]
Abstract
The goldfish (Carassius auratus) exhibits a remarkable capacity to survive and remain active under prolonged and severe hypoxia, making it a good model for studying cardiac function when oxygen availability is a limiting factor. Under hypoxia, the goldfish heart increases its performance, representing a putative component of hypoxia tolerance; however, the underlying mechanisms have not yet been elucidated. Here, we aimed to investigate the role of β3-adrenoreceptors (ARs) in the mechanisms that modulate goldfish heart performance along with the impact of oxygen levels. By western blotting analysis, we found that the goldfish heart expresses β3-ARs, and this expression increases under hypoxia. The effects of β3-AR stimulation were analysed by using an ex vivo working heart preparation. Under normoxia, the β3-AR-selective agonist BRL37344 (10-12 to 10-7 mol l-1) elicited a concentration-dependent increase of contractility that was abolished by a specific β3-AR antagonist (SR59230A; 10-8 mol l-1), but not by α/β1/β2-AR inhibitors (phentolamine, nadolol and ICI118,551; 10-7 mol l-1). Under acute hypoxia, BRL37344 did not affect goldfish heart performance. However, SR59230A, but not phentolamine, nadolol or ICI118,551, abolished the time-dependent enhancement of contractility that characterizes the hypoxic goldfish heart. Under both normoxia and hypoxia, adenylate cyclase and cAMP were found to be involved in the β3-AR-dependent downstream transduction pathway. In summary, we show the presence of functional β3-ARs in the goldfish heart, whose activation modulates basal performance and contributes to a hypoxia-dependent increase of contractility.
Collapse
Affiliation(s)
- Serena Leo
- Dept of Biology, Ecology and Earth Sciences (BEST), University of Calabria, Arcavacata di Rende (CS), Italy
| | - Alfonsina Gattuso
- Dept of Biology, Ecology and Earth Sciences (BEST), University of Calabria, Arcavacata di Rende (CS), Italy
| | - Rosa Mazza
- Dept of Biology, Ecology and Earth Sciences (BEST), University of Calabria, Arcavacata di Rende (CS), Italy
| | - Mariacristina Filice
- Dept of Biology, Ecology and Earth Sciences (BEST), University of Calabria, Arcavacata di Rende (CS), Italy
| | - Maria Carmela Cerra
- Dept of Biology, Ecology and Earth Sciences (BEST), University of Calabria, Arcavacata di Rende (CS), Italy
| | - Sandra Imbrogno
- Dept of Biology, Ecology and Earth Sciences (BEST), University of Calabria, Arcavacata di Rende (CS), Italy
| |
Collapse
|
14
|
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: 15] [Impact Index Per Article: 3.0] [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.
Collapse
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
| |
Collapse
|
15
|
Is the teleost heart oxygen limited? - Insights using "hyperoxic" incubations of contracting cardiac tissue from rainbow trout. Comp Biochem Physiol A Mol Integr Physiol 2019; 231:124-130. [PMID: 30738911 DOI: 10.1016/j.cbpa.2019.01.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 01/24/2019] [Accepted: 01/29/2019] [Indexed: 11/22/2022]
Abstract
Considerable effort has been devoted to understanding the negative effects of reduced PO2 on cardiac function. Much less is known about the impacts of elevated PO2 (hyperoxia) on cardiac performance and energetics, especially in fishes. The fish heart is of particular interest because cardiac dependence on oxygen is extremely variable between species and the early evolution of fish occurred when atmospheric PO2 was higher than current conditions. Although extracellular PO2 is variable and normally does not exceed 21 kPa, recent evidence suggests that teleost cardiac function is stimulated at supraphysiological PO2 values. The purpose of this study was to address whether cardiac contractility and energy metabolism is responsive to elevated PO2 values in sexually-immature female rainbow trout. Isometric force development (contractility) and oxygen consumption (V̇O2) were recorded in electrically-paced ventricular preparations. Contractility and V̇O2decreased when superfusate PO2 was decreased from ~70 kPa to 57 kPa or 45 kPa. However, PO2 calculated at the preparation core was always above 18 kPa. This estimate, along with complete recovery of contractility and V̇O2 at ~70 kPa, suggests that decreases observed in cardiac performance were not due to tissue hypoxia at the lower PO2 levels. In conclusion, the heart of female rainbow trout may be oxygen-limited in vitro and this study raises new questions about the choice of appropriate PO2 for experimentation, the relevance of elevated and varying PO2 to measurements of cardiac performance, and the possible existence of an oxygen sensor within rainbow trout cardiomyocytes.
Collapse
|
16
|
Joyce W, Williams CJA, Iversen S, Henriksen PG, Bayley M, Wang T. The effects of endogenous and exogenous catecholamines on hypoxic cardiac performance in red-bellied piranhas. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2018; 331:27-37. [DOI: 10.1002/jez.2233] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 08/01/2018] [Accepted: 08/24/2018] [Indexed: 11/06/2022]
Affiliation(s)
- William Joyce
- Department of Zoophysiology; Aarhus University; Aarhus Denmark
| | | | - Sofie Iversen
- Department of Zoophysiology; Aarhus University; Aarhus Denmark
| | | | - Mark Bayley
- Department of Zoophysiology; Aarhus University; Aarhus Denmark
| | - Tobias Wang
- Department of Zoophysiology; Aarhus University; Aarhus Denmark
- Aarhus Institute of Advanced Studies; Aarhus University; Aarhus Denmark
| |
Collapse
|
17
|
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.
Collapse
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
| |
Collapse
|
18
|
Roberts JC, Syme DA. Effects of epinephrine exposure on contractile performance of compact and spongy myocardium from rainbow trout (Oncorhynchus mykiss) during hypoxia. FISH PHYSIOLOGY AND BIOCHEMISTRY 2018; 44:49-62. [PMID: 28795283 DOI: 10.1007/s10695-017-0412-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 07/21/2017] [Indexed: 06/07/2023]
Abstract
Hypoxia results in elevated circulating epinephrine for many fish species, and this is likely important for maintaining cardiac function. The aims of this study were to assess how hypoxia impacts contractile responses of ventricular compact and spongy myocardium from rainbow trout (Oncorhynchus mykiss) and to assess how and if epinephrine may protect myocardial performance from a depressive effect of hypoxia. Work output and maximum contraction rate of isolated preparations of spongy and compact ventricular myocardium from rainbow trout were measured. Tissues were exposed to the blood PO2 that they experience in vivo during environmental normoxia and hypoxia and also to low (5 nM) and high (500 nM) levels of epinephrine in 100% air saturation (PO2 20.2 kPa) and during hypoxia (PO2 2 kPa, 10% air saturation). It was hypothesized that hypoxia would result in a decrease in work output and maximum contraction rate in both tissue types, but that epinephrine exposure would mitigate the effect. Hypoxia resulted in a decline in net work output of both tissue types, but a decline in maximum contraction rate of only compact myocardium. Epinephrine restored the maximum contraction rate of compact myocardium in hypoxia, appeared to slightly enhance work output of only compact myocardium in air saturation but surprisingly not during hypoxia, and restored net work of hypoxic spongy myocardium toward normoxic levels. These results indicate hypoxia has a similar depressive effect on both layers of ventricular myocardium, but that high epinephrine may be important for maintaining inotropy in spongy myocardium and chronotropy in compact myocardium during hypoxia.
Collapse
Affiliation(s)
- Jordan C Roberts
- Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N1N4, Canada
| | - Douglas A Syme
- Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N1N4, Canada.
| |
Collapse
|
19
|
Cox GK, Crossley DA, Stieglitz JD, Heuer RM, Benetti DD, Grosell M. Oil Exposure Impairs In Situ Cardiac Function in Response to β-Adrenergic Stimulation in Cobia (Rachycentron canadum). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:14390-14396. [PMID: 29132212 DOI: 10.1021/acs.est.7b03820] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Aqueous crude oil spills expose fish to varying concentrations of dissolved polycyclic aromatic hydrocarbons (PAHs), which can have lethal and sublethal effects. The heart is particularly vulnerable in early life stages, as PAH toxicity causes developmental cardiac abnormalities and impaired cardiovascular function. However, cardiac responses of juvenile and adult fish to acute oil exposure remain poorly understood. We sought to assess cardiac function in a pelagic fish species, the cobia (Rachycentron canadum), following acute (24 h) exposure to two ecologically relevant levels of dissolved PAHs. Cardiac power output (CPO) was used to quantify cardiovascular performance using an in situ heart preparation. Cardiovascular performance was varied using multiple concentrations of the β-adrenoceptor agonist isoproterenol (ISO) and by varying afterload pressures. Oil exposure adversely affected CPO with control fish achieving maximum CPO's (4 mW g-1 Mv) greater than that of oil-exposed fish (1 mW g-1 Mv) at ISO concentrations of 1 × 10-6 M. However, the highest concentration of ISO (1 × 10-5 M) rescued cardiac function. This indicates an interactive effect between oil-exposure and β-adrenergic stimulation and suggests if animals achieve very large increases in β-adrenergic stimulation it could play a compensatory role that may mitigate some adverse effects of oil-exposure in vivo.
Collapse
Affiliation(s)
- Georgina K Cox
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami , Miami, Florida 33149-1098, United States
| | - Dane A Crossley
- University of North Texas , Department of Biological Sciences, 1155 Union Circle, Denton, Texas 76203, United States
| | - John D Stieglitz
- Department of Marine Ecosystems and Society, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami , Miami, Florida 33149-1098, United States
| | - Rachael M Heuer
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami , Miami, Florida 33149-1098, United States
| | - Daniel D Benetti
- Department of Marine Ecosystems and Society, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami , Miami, Florida 33149-1098, United States
| | - Martin Grosell
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami , Miami, Florida 33149-1098, United States
| |
Collapse
|
20
|
|
21
|
Prystay TS, Eliason EJ, Lawrence MJ, Dick M, Brownscombe JW, Patterson DA, Crossin GT, Hinch SG, Cooke SJ. The influence of water temperature on sockeye salmon heart rate recovery following simulated fisheries interactions. CONSERVATION PHYSIOLOGY 2017; 5:cox050. [PMID: 28928974 PMCID: PMC5597901 DOI: 10.1093/conphys/cox050] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 06/21/2017] [Accepted: 07/25/2017] [Indexed: 05/20/2023]
Abstract
Selective harvest policies have been implemented in North America to enhance the conservation of Pacific salmon (Oncorhynchus spp.) stocks, which has led to an increase in the capture and release of fish by all fishing sectors. Despite the immediate survival benefits, catch-and-release results in capture stress, particularly at high water temperatures, and this can result in delayed post-release mortality minutes to days later. The objective of this study was to evaluate how different water temperatures influenced heart rate disturbance and recovery of wild sockeye salmon (Oncorhynchus nerka) following fisheries interactions (i.e. exhaustive exercise). Heart rate loggers were implanted into Fraser River sockeye salmon prior to simulated catch-and-release events conducted at three water temperatures (16°C, 19°C and 21°C). The fisheries simulation involved chasing logger-implanted fish in tanks for 3 min, followed by a 1 min air exposure. Neither resting nor routine heart rate differed among temperature treatments. In response to the fisheries simulation, peak heart rate increased with temperature (16°C = 91.3 ± 1.3 beats min-1; 19°C = 104.9 ± 2.0 beats min-1 and 21°C = 117 ± 1.3 beats min-1). Factorial heart rate and scope for heart rate were highest at 21°C and lowest at 16°C, but did not differ between 19°C and 21°C. Temperature affected the initial rate of cardiac recovery but not the overall duration (~10 h) such that the rate of energy expenditure during recovery increased with temperature. These findings support the notion that in the face of climate change, efforts to reduce stress at warmer temperatures will be necessary if catch-and-release practices are to be an effective conservation strategy.
Collapse
Affiliation(s)
- Tanya S. Prystay
- Department of Biology, Dalhousie University, Halifax B3H 4R2, Canada
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental Science, Carleton University, Ottawa K1S 5B6, Canada
- Corresponding author: Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada.
| | - Erika J. Eliason
- Department of Ecology, Evolution and Marine Biology, University of California, CA 93106, USA
| | - Michael J. Lawrence
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental Science, Carleton University, Ottawa K1S 5B6, Canada
| | - Melissa Dick
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental Science, Carleton University, Ottawa K1S 5B6, Canada
| | - Jacob W. Brownscombe
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental Science, Carleton University, Ottawa K1S 5B6, Canada
| | - David A. Patterson
- Fisheries and Oceans Canada, School of Resource and Environmental Management, Simon Fraser University, Burnaby V2R 5B6, Canada
| | - Glenn T. Crossin
- Department of Biology, Dalhousie University, Halifax B3H 4R2, Canada
| | - Scott G. Hinch
- Department of Forest and Conservation Sciences, University of British Columbia, Vancouver V6T 1Z4, Canada
| | - Steven J. Cooke
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental Science, Carleton University, Ottawa K1S 5B6, Canada
| |
Collapse
|
22
|
|
23
|
|
24
|
Goulding AT, Farrell AP. Quantification of ventricular β2 -adrenoceptor density and ligand binding affinity in wild sockeye salmon Oncorhynchus nerka smolts using a novel modification to the tritiated ligand technique. JOURNAL OF FISH BIOLOGY 2016; 88:2081-2087. [PMID: 27095288 DOI: 10.1111/jfb.12977] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 02/12/2016] [Indexed: 06/05/2023]
Abstract
A new, image-based, tritiated ligand technique for measuring cardiac β2 -adrenoceptor (β2 -AR) binding characteristics was developed and validated with adult rainbow trout Oncorhynchus mykiss hearts so that the tissue limitation of traditional receptor binding techniques could be overcome and measurements could be made in hearts nearly 14-times smaller than previously used. The myocardial cell-surface (functional) β2 -AR density of O. nerka smolts sampled at the headwaters of the Chilko River was 54·2 fmol mg protein(-1) and about half of that previously found in return migrating adults of the same population, but still more than twice that of adult hatchery O. mykiss (21·1 fmol mg protein(-1) ). This technique now opens the possibility of investigating cardiac receptor density in a much wider range of fish species and life stages.
Collapse
Affiliation(s)
- A T Goulding
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada
| | - A P Farrell
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada
- Faculty of Land and Food Systems, University of British Columbia, 2357 Main Mall, Vancouver, BC, V6T 1Z4, Canada
| |
Collapse
|
25
|
Elasmobranch Cardiovascular System. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/b978-0-12-801286-4.00001-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
26
|
Ekström A, Jutfelt F, Sandblom E. Effects of autonomic blockade on acute thermal tolerance and cardioventilatory performance in rainbow trout, Oncorhynchus mykiss. J Therm Biol 2014; 44:47-54. [PMID: 25086973 DOI: 10.1016/j.jtherbio.2014.06.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 05/30/2014] [Accepted: 06/02/2014] [Indexed: 10/25/2022]
Abstract
Predicted future increases in global temperature may impose challenges for ectothermic animals like fish, but the physiological mechanisms determining the critical thermal maximum (CTmax) are not well understood. One hypothesis suggests that impaired cardiac performance, limited by oxygen supply, is an important underlying mechanism. Since vagal bradycardia is suggested to improve cardiac oxygenation and adrenergic stimulation may improve cardiac contractility and protect cardiac function at high temperatures, we predicted that pharmacological blockade of cardiac autonomic control would lower CTmax. Rainbow trout was instrumented with a flow probe and a ventilation catheter for cardioventilatory recordings and exposed to an acute thermal challenge until CTmax following selective pharmacological blockade of muscarinic or β-adrenergic receptors. Contrary to our prediction, CTmax (~26°C) was unchanged between treatments. While β-adrenergic blockade reduced heart rate it did not impair cardiac stroke volume across temperatures suggesting that compensatory increases in cardiac filling pressure may serve to maintain cardiac output. While warming resulted in significant tachycardia and increased cardiac output, a high cholinergic tone on the heart was observed at temperatures approaching CTmax. This may represent a mechanism to maintain scope for heart rate and possibly to improve myocardial contractility and oxygen supply at high temperatures. This is the first study evaluating the importance of autonomic cardiac control on thermal tolerance in fish. While no effects on CTmax were observed, this study raises important questions about the underlying mechanisms determining thermal tolerance limits in ectothermic animals.
Collapse
Affiliation(s)
- Andreas Ekström
- Department of Biology and Environmental Sciences, University of Gothenburg, Gothenburg Sweden.
| | - Fredrik Jutfelt
- Department of Biology and Environmental Sciences, University of Gothenburg, Gothenburg Sweden; The Sven Lovén Centre for Marine Sciences, Kristineberg, Fiskebäckskil, Sweden
| | - Erik Sandblom
- Department of Biology and Environmental Sciences, University of Gothenburg, Gothenburg Sweden
| |
Collapse
|
27
|
Farrell A, Altimiras J, Franklin C, Axelsson M. Niche expansion of the shorthorn sculpin (Myoxocephalus scorpius) to Arctic waters is supported by a thermal independence of cardiac performance at low temperature. CAN J ZOOL 2013. [DOI: 10.1139/cjz-2013-0038] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiovascular adaptations that permit successful exploitation of polar marine waters by fish requires a capacity to negate or compensate for the depressive effects of low temperatures on physiological processes. Here, we examined the effects of acute and chronic temperature change on the maximum cardiac performance of shorthorn sculpin (Myoxocephalus scorpius (L., 1758)) captured above the Arctic Circle. Our aim was to establish if the sculpin’s success at low temperatures was achieved through thermal independence of cardiac function or via thermal compensation as a result of acclimation. Maximum cardiac performance was assessed at both 1 and 6 °C with a working perfused heart preparation that was obtained after fish had been acclimated to either 1 or 6 °C. Thus, tests were performed at the fish’s acclimation temperature and with an acute temperature change. Maximum cardiac output, which was relatively large (>50 mL·min−1·kg−1 body mass) for a benthic fish at a frigid temperature, was found to be independent of both acclimation temperature and test temperature. While maximum β-adrenergic stimulation produced positive chronotropy at both acclimation temperatures, inotropic effects were weak or absent. We conclude that thermal independence of cardiac performance at low temperature likely facilitated the exploitation of polar waters by the shorthorn sculpin.
Collapse
Affiliation(s)
- A.P. Farrell
- Department of Zoology and Faculty of Land and Food Systems, 6270 University Boulevard, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - J. Altimiras
- IFM Biology, Division of Zoology, University of Linköping, SE-58183 Linköping, Sweden
| | - C.E. Franklin
- School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - M. Axelsson
- University of Gothenburg, Department of Biological and Environmental Sciences, SE-405 30 Gothenburg, Sweden
| |
Collapse
|
28
|
Effects of fatty acid provision during severe hypoxia on routine and maximal performance of the in situ tilapia heart. J Comp Physiol B 2013; 183:773-85. [PMID: 23539326 DOI: 10.1007/s00360-013-0750-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 02/06/2013] [Accepted: 03/04/2013] [Indexed: 10/27/2022]
Abstract
The ability to maintain stable cardiac function during environmental hypoxia exposure is crucial for hypoxia tolerance in animals and depends upon the maintenance of cardiac energy balance as well as the state of the heart's extracellular environment (e.g., availability of metabolic fuels). Hypoxic depression of plasma [non-esterified fatty acids] (NEFA), an important cardiac aerobic fuel, is a common response in many species of hypoxia-tolerant fishes, including tilapia. We tested the hypothesis that decreased plasma [NEFA] is important for maintaining stable cardiac function during and following hypoxia exposure, based on the premise that continued reliance upon cardiac fatty acid metabolism under such conditions could impair cardiac function. We examined the effect of severe hypoxia exposure (PO2 < 0.2 kPa) on routine and maximum performance of the in situ perfused tilapia heart under conditions of routine (400 μmol L(-1)) and low (75 μmol L(-1)) [palmitate], which mimicked the in vivo levels of plasma [NEFA] found in normoxic and hypoxic tilapia, respectively. Under both concentrations of palmitate, the in situ tilapia heart showed exceptional hypoxic performance as a result of a high maximum glycolytic potential, confirming our previous results using a perfusate without fatty acids. We additionally provide evidence suggesting that non-contractile ATP demand is depressed in tilapia heart during hypoxia exposure. Cardiac performance during and following severe hypoxia exposure was unaffected by the level of palmitate. Thus, we conclude that hypoxic depression of plasma [NEFA] in fishes does not play a role in cardiac hypoxia tolerance.
Collapse
|
29
|
Petersen LH, Needham SL, Burleson ML, Overturf MD, Huggett DB. Involvement of β3-adrenergic receptors in in vivo cardiovascular regulation in rainbow trout (Oncorhynchus mykiss). Comp Biochem Physiol A Mol Integr Physiol 2013; 164:291-300. [DOI: 10.1016/j.cbpa.2012.11.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 10/30/2012] [Accepted: 11/01/2012] [Indexed: 01/10/2023]
|
30
|
Lague SL, Speers-Roesch B, Richards JG, Farrell AP. Exceptional cardiac anoxia tolerance in tilapia (Oreochromis hybrid). ACTA ACUST UNITED AC 2012; 215:1354-65. [PMID: 22442374 DOI: 10.1242/jeb.063362] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Anoxic survival requires the matching of cardiac ATP supply (i.e. maximum glycolytic potential, MGP) and demand (i.e. cardiac power output, PO). We examined the idea that the previously observed in vivo downregulation of cardiac function during exposure to severe hypoxia in tilapia (Oreochromis hybrid) represents a physiological strategy to reduce routine PO to within the heart's MGP. The MGP of the ectothermic vertebrate heart has previously been suggested to be ∼70 nmol ATP s(-1) g(-1), sustaining a PO of ∼0.7 mW g(-1) at 15°C. We developed an in situ perfused heart preparation for tilapia (Oreochromis hybrid) and characterized the routine and maximum cardiac performance under both normoxic (>20 kPa O(2)) and severely hypoxic perfusion conditions (<0.20 kPa O(2)) at pH 7.75 and 22°C. The additive effects of acidosis (pH 7.25) and chemical anoxia (1 mmol l(-1) NaCN) on cardiac performance in severe hypoxia were also examined. Under normoxic conditions, cardiac performance and myocardial oxygen consumption rate were comparable to those of other teleosts. The tilapia heart maintained a routine normoxic cardiac output (Q) and PO under all hypoxic conditions, a result that contrasts with the hypoxic cardiac downregulation previously observed in vivo under less severe conditions. Thus, we conclude that the in vivo downregulation of routine cardiac performance in hypoxia is not needed in tilapia to balance cardiac energy supply and demand. Indeed, the MGP of the tilapia heart proved to be quite exceptional. Measurements of myocardial lactate efflux during severe hypoxia were used to calculate the MGP of the tilapia heart. The MGP was estimated to be 172 nmol ATP s(-1) g(-1) at 22°C, and allowed the heart to generate a PO(max) of at least ∼3.1 mW g(-1), which is only 30% lower than the PO(max) observed with normoxia. Even with this MGP, the additional challenge of acidosis during severe hypoxia decreased maximum ATP turnover rate and PO(max) by 30% compared with severe hypoxia alone, suggesting that there are probably direct effects of acidosis on cardiac contractility. We conclude that the high maximum glycolytic ATP turnover rate and levels of PO, which exceed those measured in other ectothermic vertebrate hearts, probably convey a previously unreported anoxia tolerance of the tilapia heart, but a tolerance that may be tempered in vivo by the accumulation of acidotic waste during anoxia.
Collapse
Affiliation(s)
- Sabine L Lague
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada, V6T 1Z4.
| | | | | | | |
Collapse
|
31
|
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%.
Collapse
Affiliation(s)
- S Ballesta
- University of British Columbia, 2357 Main Mall, Vancouver, BC, V6T 1Z4 Canada.
| | | | | |
Collapse
|
32
|
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.
Collapse
|
33
|
Petersen LH, Gamperl AK. Cod (Gadus morhua) cardiorespiratory physiology and hypoxia tolerance following acclimation to low-oxygen conditions. Physiol Biochem Zool 2011; 84:18-31. [PMID: 21050128 DOI: 10.1086/657286] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Previous research has shown that hypoxia-acclimated Atlantic cod (Gadus morhua) have significantly reduced cardiac function but can consume more oxygen for a given cardiac output (Q). However, it is not known (1) which physiological changes permit a greater "oxygen pulse" (oxygen consumed per mL of blood pumped) in hypoxia-acclimated individuals or (2) whether chronic exposure to low-oxygen conditions improves the hypoxia tolerance of cod. Thus, we exposed normoxia- and hypoxia-acclimated (> 6 wk at a water oxygen partial pressure [P(w)O(2)] ~8-9 kPa) cod to a graded normoxia challenge until loss of equilibrium occurred while recording the following cardiorespiratory variables: oxygen consumption (MO(2)), ventilatory rate, cardiac function (Q, heart rate f(H), and stroke volume S(V)), ventral aortic blood pressure (P(VA)), venous oxygen partial pressure (P(v)O(2)) and oxygen content (C(v)O(2)), plasma catecholamines, and blood hemoglobin ([Hb]) and hematocrit (Hct). In addition, we performed in vitro hemoglobin oxygen binding curves to examine whether hypoxia acclimation influences hemoglobin functional properties. Numerous physiological adjustments occurred in vivo during the > 6 wk of hypoxia acclimation: that is, increased f(H), decreased S(V) and Q, elevated [Hb], enhanced tissue oxygen extraction (by 10% at a P(w)O(2) of 20 kPa), and a more robust stress response as evidenced by circulating catecholamine levels that were two to eight times higher when fish were acutely exposed to severe hypoxia. In contrast, chronic hypoxia had no significant effect on the affinity of hemoglobin for oxygen, on in vitro hemoglobin oxygen carrying capacity, or on the cod's hypoxia tolerance (H(crit); the P(w)O(2) at which the fish lost equilibrium, which was 4.3 ± 0.2 and 4.8 ± 0.3 kPa in normoxia- and hypoxia-acclimated fish, respectively). These data suggest that while chronic hypoxia results in numerous physiological adjustments, these changes do not improve the cod's capacity to tolerate low-oxygen conditions.
Collapse
Affiliation(s)
- L H Petersen
- Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, A1C 5S7 Newfoundland, Canada
| | | |
Collapse
|
34
|
Stecyk JAW, Larsen BC, Nilsson GE. Intrinsic contractile properties of the crucian carp (Carassius carassius) heart during anoxic and acidotic stress. Am J Physiol Regul Integr Comp Physiol 2011; 301:R1132-42. [PMID: 21795637 DOI: 10.1152/ajpregu.00372.2010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The crucian carp (Carassius carassius) seems unique among vertebrates in its ability to maintain cardiac performance during prolonged anoxia. We investigated whether this phenomenon arises in part from a myocardium tolerant to severe acidosis or because the anoxic crucian carp heart may not experience a severe extracellular acidosis due to the fish's ability to convert lactate to ethanol. Spontaneously contracting heart preparations from cold-acclimated (6-8°C) carp were exposed (at 6.5°C) to graded or ungraded levels of acidosis under normoxic or anoxic conditions and intrinsic contractile performance was assessed. Our results clearly show that the carp heart is tolerant of acidosis as long as oxygen is available. However, heart rate and contraction kinetics of anoxic hearts were severely impaired when extracellular pH was decreased below 7.4. Nevertheless, the crucian carp heart was capable of recovering intrinsic contractile performance upon reoxygenation regardless of the severity of the anoxic + acidotic insult. Finally, we show that increased adrenergic stimulation can ameliorate, to a degree, the negative effects of severe acidosis on the intrinsic contractile properties of the anoxic crucian carp heart. Combined, these findings indicate an avoidance of severe extracellular acidosis and adrenergic stimulation are two important factors protecting the intrinsic contractile properties of the crucian carp heart during prolonged anoxia, and thus likely facilitate the ability of the anoxic crucian carp to maintain cardiac pumping.
Collapse
Affiliation(s)
- Jonathan A W Stecyk
- Physiology Programme, Dept. of Molecular Biosciences, Univ. of Oslo, PO Box 1041, N-0316, Oslo, Norway.
| | | | | |
Collapse
|
35
|
Miller SC, Gillis TE, Wright PA. The ontogeny of regulatory control of the rainbow trout (Oncorhynchus mykiss) heart and how this is influenced by chronic hypoxia exposure. J Exp Biol 2011; 214:2065-72. [DOI: 10.1242/jeb.054825] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Salmonid embryos develop in cool waters over relatively long periods of time. Interestingly, hypoxic conditions have been found to be relatively common in some nesting sites (redds). The goals of this study were to determine the ontogeny of cardiac regulation in rainbow trout early life stages and how this is influenced by chronic hypoxia. The heart rate response to cholinergic and adrenergic receptor stimulation or inhibition was measured in individuals reared in normoxic (100% O2 saturation) or hypoxic (30% O2 saturation) conditions from fertilization to embryonic stages 22, 26 and 29, and larval stages 30 and 32. In normoxia, heart rate increased in response to β-adrenergic receptor stimulation (isoproterenol) as early as embryonic stage 22, and decreased with the antagonist propranolol after this stage. Cholinergic stimulation (acetylcholine) was ineffective at all stages, but atropine (acetylcholine antagonist) increased heart rate at larval stage 32. This demonstrates that cardiac β-adrenergic receptors are functional at early life stages, while cholinergic receptors are not responsive until after hatching. Collectively, embryos had cardio-acceleration control mechanisms in place just after the heartbeat stage, while cardio-inhibitory control was not functional until after hatching. Chronic hypoxia exposure triggered bradycardia, increased the response to adrenergic stimulation in embryos and larvae, and delayed the onset of cholinergic control in larvae. In non-motile stages, therefore, survival in chronic low oxygen may depend on the ability to alter the cardiac ontogenic program to meet the physiological requirements of the developing fish.
Collapse
Affiliation(s)
- Silvana C. Miller
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Todd E. Gillis
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Patricia A. Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, N1G 2W1
| |
Collapse
|
36
|
Baker DW, Hanson LM, Farrell AP, Brauner CJ. Exceptional CO₂ tolerance in white sturgeon (Acipenser transmontanus) is associated with protection of maximum cardiac performance during hypercapnia in situ. Physiol Biochem Zool 2011; 84:239-48. [PMID: 21527814 DOI: 10.1086/660038] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
White sturgeon rank among the most CO₂-tolerant fish species examined to date. We investigated whether this exceptional CO₂ tolerance extended to the heart, an organ generally viewed as acidosis intolerant. Maximum cardiac output (Q(max)) and maximum cardiac power output (PO(max)) were assessed using a working, perfused, in situ heart preparation. Exposure to a Pco₂ of 3 kPa for 20 min had no significant effect on maximum cardiac performance, while exposure to 6-kPa Pco₂ reduced heart rate, Q(max), PO(max), and rate of ventricular force generation (F(O)) by 23%, 28%, 26%, and 18%, respectively; however, full recovery was observed in all these parameters upon return to control conditions. These modest impairments during exposure to 6-kPa Pco₂ were associated with partially compensated intracellular ventricular acidosis. Maximum adrenergic stimulation (500 nmol L⁻¹ adrenaline) during 6-kPa Pco₂ protected maximum cardiac performance via increased inotropy (force of contraction) without affecting heart rate. Exposure to higher CO₂ levels associated with morbidity in vivo (i.e., 8-kPa Pco₂) induced arrhythmia and a reduction in stroke volume during power assessment. Clearly, white sturgeon hearts are able to increase cardiac performance during severe hypercapnia that is lethal to other fishes. Future work focusing on atypical aspects of sturgeon cardiac function, including the lack of chronotropic response to adrenergic stimulation during hypercapnia, is warranted.
Collapse
Affiliation(s)
- Daniel W Baker
- School of Biological Science, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
| | | | | | | |
Collapse
|
37
|
Petersen LH, Gamperl AK. Effect of acute and chronic hypoxia on the swimming performance, metabolic capacity and cardiac function of Atlantic cod (Gadus morhua). ACTA ACUST UNITED AC 2010; 213:808-19. [PMID: 20154197 DOI: 10.1242/jeb.033746] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Low water oxygen content (hypoxia) is a common feature of many freshwater and marine environments. However, we have a poor understanding of the degree to which diminished cardiac function contributes to the reduction in fish swimming performance concomitant with acute exposure to hypoxia, or how fish cardiorespiratory physiology is altered by, or adapts to, chronic hypoxia. Thus, we acclimated adult Atlantic cod (Gadus morhua) to either approximately 8-9 kPa O(2) (40-45% air saturation) or approximately 21 kPa O(2) (100% air saturation; normoxia) for 6-12 weeks at 10 degrees C, and subsequently measured metabolic variables [routine oxygen consumption (M(O(2)), maximum (M(O(2)), metabolic scope] and cardiac function (cardiac output, Q; heart rate, f(H); and stroke volume, V(S)) in these fish during critical swimming speed (U(crit)) tests performed at both levels of water oxygenation. Although surgery (flow probe implantation) reduced the U(crit) of normoxia-acclimated cod by 14% (from 1.74 to 1.50 BL s(-1)) under normoxic conditions, exposure to acute hypoxia lowered the U(crit) of both groups (surgery and non-surgery) by approximately 30% (to 1.23 and 1.02 BL s(-1), respectively). This reduction in swimming performance was associated with large decreases in maximum M(O(2)) and metabolic scope (> or = 50%), and maximum f(H) and Q (by 16 and 22%), but not V(S). Long-term acclimation to hypoxia resulted in a significant elevation in normoxic metabolic rate as compared with normoxia-acclimated fish (by 27%), but did not influence normoxic or hypoxic values for U(crit), maximum M(O(2)) or metabolic scope. This was surprising given that resting and maximum values for Q were significantly lower in hypoxia-acclimated cod at both levels of oxygenation, because of lower values for V(S). However, hypoxia-acclimated cod were able to consume more oxygen for a given cardiac output. These results provide important insights into how fish cardiorespiratory physiology is impacted by short-term and prolonged exposure to hypoxia, and further highlight the tremendous capacity of the fish cardiorespiratory system to deal with environmental challenges.
Collapse
Affiliation(s)
- L H Petersen
- Ocean Sciences Centre, Memorial University of Newfoundland, St John's, NL, Canada, A1C 5S7
| | | |
Collapse
|
38
|
Petersen LH, Gamperl AK. In situ cardiac function in Atlantic cod (Gadus morhua): effects of acute and chronic hypoxia. J Exp Biol 2010; 213:820-30. [DOI: 10.1242/jeb.033753] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
SUMMARY
Recent in vivo experiments on Atlantic cod (Gadus morhua) acclimated to chronic hypoxia (6-12 weeks at 10°C; PwO2 ~8-9 kPa) revealed a considerable decrease in the pumping capacity of the heart. To examine whether this diminished cardiac performance was due to the direct effects of chronic moderate hypoxia on the myocardium (as opposed to alterations in neural and/or hormonal control), we measured the resting and maximum in situ function of hearts from normoxia- and hypoxia-acclimated cod: (1) when initially perfused with oxygenated saline; (2) at the end of a 15 min exposure to severe hypoxia (PO2 ~0.6 kPa); and (3) 30 min after the hearts had been reperfused with oxygenated saline. Acclimation to hypoxia did not influence resting (basal) in situ cardiac performance during oxygenated or hypoxic conditions. However, it caused a decrease in maximum cardiac output () under oxygenated conditions (from 49.5 to 40.3 ml min−1 kg−1; by 19%), that was due to diminished values for maximum stroke volume (VS) and scope for VS. Severe hypoxia reduced in both groups to ~20 ml min−1 kg−1, yet, the hearts of hypoxia-acclimated fish were better able to sustain this level of under hypoxia, and the recovery of (as compared with initial values under oxygenated conditions) was significantly improved (94% vs 83%). These data show that acclimation to hypoxia has a direct effect on cod myocardial function and/or physiology, and suggest that the cod heart shows some adaptations to prolonged hypoxia.
Collapse
Affiliation(s)
- L. H. Petersen
- Ocean Sciences Centre, Memorial University of Newfoundland, St John's, NL, Canada, A1C 5S7
| | - A. K. Gamperl
- Ocean Sciences Centre, Memorial University of Newfoundland, St John's, NL, Canada, A1C 5S7
| |
Collapse
|
39
|
Farrell AP. Environment, antecedents and climate change: lessons from the study of temperature physiology and river migration of salmonids. J Exp Biol 2009; 212:3771-80. [PMID: 19915118 DOI: 10.1242/jeb.023671] [Citation(s) in RCA: 200] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Summary
Animal distributions are shaped by the environment and antecedents. Here I show how the temperature dependence of aerobic scope (the difference between maximum and minimum rates of oxygen uptake) is a useful tool to examine the fundamental temperature niches of salmonids and perhaps other fishes. Although the concept of aerobic scope has been recognized for over half a century, only recently has sufficient evidence accumulated to provide a mechanistic explanation for the optimal temperature of salmonids. Evidence suggests that heart rate is the primary driver in supplying more oxygen to tissues as demand increases exponentially with temperature. By contrast, capacity functions (i.e. cardiac stroke volume, tissue oxygen extraction and haemoglobin concentration) are exploited only secondarily if at all, with increasing temperature, and then perhaps only at a temperature nearing that which is lethal to resting fish. Ultimately, however, heart rate apparently becomes a weak partner for the cardiorespiratory oxygen cascade when temperature increases above the optimum for aerobic scope. Thus, the upper limit for heart rate may emerge as a valuable, but simple predictor of optimal temperature in active animals, opening the possibility of using biotelemetry of heart rate in field situations to explore properly the full interplay of environmental factors on aerobic scope. An example of an ecological application of these physiological discoveries is provided using the upriver migration of adult sockeye salmon, which have a remarkable fidelity to their spawning areas and appear to have an optimum temperature for aerobic scope that corresponds to the river temperatures experienced by their antecedents. Unfortunately, there is evidence that this potential adaptation is incompatible with the rapid increase in river temperature presently experienced by salmon as a result of climate change. By limiting aerobic scope, river temperatures in excess of the optimum for aerobic scope directly impact upriver spawning migration and hence lifetime fecundity. Thus, use of aerobic scope holds promise for scientists who wish to make predictions on how climate change may influence animal distributions.
Collapse
Affiliation(s)
- A. P. Farrell
- Zoology Department, 6270 University Boulevard, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| |
Collapse
|
40
|
Farrell AP, Eliason EJ, Sandblom E, Clark TD. Fish cardiorespiratory physiology in an era of climate changeThe present review is one of a series of occasional review articles that have been invited by the Editors and will feature the broad range of disciplines and expertise represented in our Editorial Advisory Board. CAN J ZOOL 2009. [DOI: 10.1139/z09-092] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This review examines selected areas of cardiovascular physiology where there have been impressive gains of knowledge and indicates fertile areas for future research. Because arterial blood is usually fully saturated with oxygen, increasing cardiac output is the only means for transferring substantially more oxygen to tissues. Consequently, any behavioural or environmental change that alters oxygen uptake typically involves a change in cardiac output, which in fishes can amount to a threefold change. During exercise, not all fishes necessarily have the same ability as salmonids to increase cardiac output by increasing stroke volume; they rely more on increases in heart rate instead. The benefits associated with increasing cardiac output via stroke volume or heart rate are unclear. Regardless, all fishes examined so far show an exquisite cardiac sensitivity to filling pressure and the cellular basis for this heightened cardiac stretch sensitivity in fish is being unraveled. Even so, a fully integrated picture of cardiovascular functioning in fishes is hampered by a dearth of studies on venous circulatory control. Potent positive cardiac inotropy involves stimulation of sarcolemmal β-adrenoceptors, which increases the peak trans-sarcolemmal current for calcium and the intracellular calcium transient available for binding to troponin C. However, adrenergic sensitivity is temperature-dependent in part through effects on membrane currents and receptor density. The membrane currents contributing to the pacemaker action potential are also being studied but remain a prime area for further study. Why maximum heart rate is limited to a low rate in most fishes compared with similar-sized mammals, even when Q10 effects are considered, remains a mystery. Fish hearts have up to three oxygen supply routes. The degree of coronary capillarization circulation is of primary importance to the compact myocardium, unlike the spongy myocardium, where venous oxygen partial pressure appears to be the critical factor in terms of oxygen delivery. Air-breathing fishes can boost the venous oxygen content and oxygen partial pressure by taking an air breath, thereby providing a third myocardial oxygen supply route that perhaps compensates for the potentially precarious supply to the spongy myocardium during hypoxia and exercise. In addition to venous hypoxemia, acidemia and hyperkalemia can accompany exhaustive exercise and acute warming, perhaps impairing the heart were it not for a cardiac protection mechanism afforded by β-adrenergic stimulation. With warming, however, a mismatch between an animal’s demand for oxygen (a Q10 effect) and the capacity of the circulatory and ventilatory systems to delivery this oxygen develops beyond an optimum temperature. At temperature extremes in salmon, it is proposed that detrimental changes in venous blood composition, coupled with a breakdown of the cardiac protective mechanism, is a potential mechanism to explain the decline in maximum and cardiac arrhythmias that are observed. Furthermore, the fall off in scope for heart rate and cardiac output is used to explain the decrease in aerobic scope above the optimum temperature, which may then explain the field observation that adult sockeye salmon ( Oncorhynchus nerka (Walbaum in Artedi, 1792)) have difficulty migrating to their spawning area at temperatures above their optimum. Such mechanistic linkages to lifetime fitness, whether they are cardiovascular or not, should assist with predictions in this era of global climate change.
Collapse
Affiliation(s)
- A. P. Farrell
- Department of Zoology and Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - E. J. Eliason
- Department of Zoology and Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - E. Sandblom
- Department of Zoology and Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - T. D. Clark
- Department of Zoology and Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| |
Collapse
|
41
|
Hanson LM, Baker DW, Kuchel LJ, Farrell AP, Val AL, Brauner CJ. Intrinsic mechanical properties of the perfused armoured catfish heart with special reference to the effects of hypercapnic acidosis on maximum cardiac performance. J Exp Biol 2009; 212:1270-6. [DOI: 10.1242/jeb.022764] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYThe armoured catfish, Pterygoplichthys pardalis, is known to be extremely tolerant of environmental hypercarbia (elevated water CO2tensions), which occurs in their natural environment. In addition, previous studies have demonstrated that during exposure to hypercarbia, P. pardalis does not exhibit extracellular pH compensation and thus the heart and other organs must continue to function despite a severe extracellular acidosis. We used an in situ perfused heart preparation to determine the effects of an extracellular hypercapnic (elevated CO2 in the animal) acidosis (1–7.5% CO2) on heart function, specifically cardiac output, power output, heart rate and stroke volume. The present study is the first to comprehensively examine cardiac function in an acidosis-tolerant teleost. When compared with control conditions, maximum cardiac performance was unaffected at levels of CO2 as high as 5%, far exceeding the hypercapnic tolerance of other teleosts. Moreover, P. pardalis exhibited only a moderate decrease(∼35%) in cardiac performance when exposed to 7.5% CO2, and full cardiac performance was restored in six out of seven hearts upon return to control conditions. Myocardial intracellular pH (pHi) was protected in situ, as has been found in vivo, and this protection extended to the highest level of CO2 (7.5%)investigated. Thus, maintained heart function during a hypercapnic acidosis in P. pardalis is probably associated with preferential pHiregulation of the heart, but ultimately is not sufficient to prevent loss of cardiac function. Our findings suggest the need for further study to elucidate the mechanisms behind this remarkable cardiac hypercapnic tolerance.
Collapse
Affiliation(s)
- Linda M. Hanson
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4 Canada
| | - Daniel W. Baker
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4 Canada
| | - Louise J. Kuchel
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4 Canada
| | - Anthony P. Farrell
- Faculty of Land and Food Systems and Department of Zoology, University of British Columbia, Vancouver, V6T 1Z4 Canada
| | - Adalberto L. Val
- Laboratory of Ecophysiology and Molecular Evolution, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil
| | - Colin J. Brauner
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4 Canada
| |
Collapse
|
42
|
Mendonça PC, Gamperl AK. Nervous and humoral control of cardiac performance in the winter flounder(Pleuronectes americanus). J Exp Biol 2009; 212:934-44. [DOI: 10.1242/jeb.027680] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
SUMMARY
Previous studies have suggested that flatfish lack adrenergic cardiac innervation and have a limited humoral adrenergic stress response. However,data on neurohormonal control of flatfish cardiac function is scarce, and has never been directly studied in vivo. Hence, we (1) injected neural and humoral antagonists into flounder (Pleuronectes americanus) in vivo to determine the contribution of autonomic innervation and circulating catecholamines to the control of resting cardiac function; (2)measured pre- and post-stress (90 s chase) catecholamine levels in this species; and (3) constructed in vivo catecholamine dose–response curves for cardiovascular function based on the results of the second experiment. In addition, we quantified the density(Bmax) and ligand-binding affinity(Kd) of flounder ventricular cell-surfaceβ-adrenoreceptors, and established whether they were ofβ 1 or β2 subtype using pharmacological antagonists. The cholinergic contribution to resting flounder heart rate was comparable to other teleosts (cholinergic tonus 26%). Interestingly, however,bretylium increased heart rate, resulting in a negative resting adrenergic tonus (–11.9%), and we were unable to demonstrate that catecholamines supported cardiac function at rest or at circulating concentrations approximating those following an exhaustive chase (adrenaline, 21 nmol l–1; noradrenaline, 14 nmol l–1). Myocardial Bmax was very high in the flounder (252.8 fmol mg–1 protein), and it appears that flounder ventricularβ-adrenoreceptors are predominantly of the β2 subtype[based on the inability of atenolol to displace [3H]CGP from theβ-adrenoreceptors, and the IC50 value for ICI 118551(1.91×10–6 mol l–1)]. However, the extremely low affinity (Kd 1.02 nmol l–1)for these receptors raises the possibility that the flounder heart is also populated by β3-adrenoreceptors.
Collapse
Affiliation(s)
- Paula C. Mendonça
- Ocean Sciences Centre, Memorial University, St John's, Canada, NL A1C 5S7
| | - A. Kurt Gamperl
- Ocean Sciences Centre, Memorial University, St John's, Canada, NL A1C 5S7
| |
Collapse
|
43
|
Steinhausen MF, Sandblom E, Eliason EJ, Verhille C, Farrell AP. The effect of acute temperature increases on the cardiorespiratory performance of resting and swimming sockeye salmon (Oncorhynchus nerka). ACTA ACUST UNITED AC 2009; 211:3915-26. [PMID: 19043063 DOI: 10.1242/jeb.019281] [Citation(s) in RCA: 169] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The mechanism underlying the decrease in aerobic scope in fish at warm temperatures is not fully understood and is the focus of this research. Our study examined oxygen uptake and delivery in resting, swimming and recovering sockeye salmon while water temperature was acutely increased from 15 degrees C to 24 degrees C in 2 degrees C h(-1) increments. Fish swam at a constant speed during the temperature change. By simultaneously measuring oxygen consumption (M(O(2))), cardiac output (Q) and the blood oxygen status of arterial and venous blood, we were able to determine where in the oxygen cascade a limitation appeared when fish stopped sustained swimming as temperature increased. High temperature fatigue of swimming sockeye salmon was not a result of a failure of either oxygen delivery to the gills or oxygen diffusion at the gills because oxygen partial pressure (P(O(2))) and oxygen content (C(O(2))) in arterial blood did not decrease with increasing temperature, as would be predicted for such limitations. Instead, arterial oxygen delivery (Ta(O(2))) was initially hampered due to a failure to adequately increase Q with increasing temperature. Subsequently, lactate appeared in the blood and venous P(O(2)) remained constant.
Collapse
Affiliation(s)
- M F Steinhausen
- Department of Zoology, University of British Columbia, 2357 Main Mall, Vancouver, BC, Canada, V6T 1Z4.
| | | | | | | | | |
Collapse
|
44
|
|
45
|
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.
Collapse
Affiliation(s)
- Jonathan A W Stecyk
- Physiology Programme, Department of Molecular Biosciences, University of Oslo, PO Box 1041, N-0316, Oslo, Norway.
| | | | | | | |
Collapse
|
46
|
Farrell AP. Tribute to P. L. Lutz: a message from the heart--why hypoxic bradycardia in fishes? ACTA ACUST UNITED AC 2008; 210:1715-25. [PMID: 17488934 DOI: 10.1242/jeb.02781] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The sensing and processing of hypoxic signals, the responses to these signals and the modulation of these responses by other physical and physiological factors are an immense topic filled with numerous novel and exciting discoveries. Nestled among these discoveries, and in contrast to mammals, is the unusual cardiac response of many fish to environmental hypoxia - a reflex slowing of heart rate. The afferent and efferent arms of this reflex have been characterised, but the benefits of the hypoxic bradycardia remain enigmatic since equivocal results have emerged from experiments examining the benefit to oxygen transfer across the gills. The main thesis developed here is that hypoxic bradycardia could afford a number of direct benefits to the fish heart, largely because the oxygen supply to the spongy myocardium is precarious (i.e. it is determined primarily by the partial pressure of oxygen in venous blood, Pv(O(2))) and, secondarily, because the fish heart has an unusual ability to produce large increases in cardiac stroke volume (V(SH)) that allow cardiac output to be maintained during hypoxic bradycardia. Among the putative benefits of hypoxic bradycardia is an increase in the diastolic residence time of blood in the lumen of the heart, which offers an advantage of increased time for diffusion, and improved cardiac contractility through the negative force-frequency effect. The increase in V(SH) will stretch the cardiac chambers, potentially reducing the diffusion distance for oxygen. Hypoxic bradycardia could also reduce cardiac oxygen demand by reducing cardiac dP/dt and cardiac power output, something that could be masked at cold temperature because of a reduced myocardial work load. While the presence of a coronary circulation in certain fishes decreases the reliance of the heart on Pv(O(2)), hypoxic bradycardia could still benefit oxygen delivery via an extended diastolic period during which peak coronary blood flow occurs. The notable absence of hypoxic bradycardia among fishes that breathe air during aquatic hypoxia and thereby raise their Pv(O(2)), opens the possibility that that the evolutionary loss of hypoxic bradycardia may have coincided with some forms of air breathing in fishes. Experiments are needed to test some of these possibilities. Ultimately, any potential benefit of hypoxic bradycardia must be placed in the proper context of myocardial oxygen supply and demand, and must consider the ability of the fish heart to support its routine cardiac power output through glycolysis.
Collapse
Affiliation(s)
- A P Farrell
- Zoology Department, 6270 University Boulevard, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
| |
Collapse
|
47
|
Chan CY, Lam WP, Wai MSM, Wang M, Foster EL, Yew DTW. Perinatal hypoxia induces anterior chamber changes in the eyes of offspring fish. J Reprod Dev 2007; 53:1159-67. [PMID: 17693701 DOI: 10.1262/jrd.19018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hypoxia is a consistent challenge for aquatic animals. It is a pressing environmental problem; hypoxia can cause cranial edema and ovarium dysfunction in fish. Although several studies have reported the effect of hypoxic insult to the visual system, the hypoxic effect on perinatal animals and in particular their offspring has yet to be elucidated. In this study, activated caspase-3 activity was investigated using immunohistochemistry in order to examine the perinatal hypoxic damage in offspring fish. Offspring were divided into groups based on different time points of sacrifice. This allowed assessment of ocular development for different age groups. The results indicated that perinatal hypoxia induced ocular developmental defects in the offspring. The defects took the form of trabecular cell death and fibre degeneration, corneal thinning and lens fibre derangement. A concomitant change in intraocular pressure was recorded by tonometer in the experimental animals compared with the controls. Further investigation should be initiated to develop strategies to prevent developmental disability due to perinatal hypoxia and to increase survivability of the offspring.
Collapse
Affiliation(s)
- Chu Yan Chan
- Department of Anatomy, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, PR China
| | | | | | | | | | | |
Collapse
|
48
|
Simonot DL, Farrell AP. Cardiac remodelling in rainbow troutOncorhynchus mykissWalbaum in response to phenylhydrazine-induced anaemia. J Exp Biol 2007; 210:2574-84. [PMID: 17601961 DOI: 10.1242/jeb.004028] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
SUMMARYWe examined the nature, extent and timing of cardiac ventricular remodelling in response to chronic, chemically induced anaemia in warm- and cold-acclimated rainbow trout Oncorhynchus mykiss. Chronic anaemia was induced by bi-weekly injections of phenylhydrazine hydrochloride (PHZ) and resulted in transient but large decreases in haematocrit (Hct) and haemoglobin concentration. After 2 weeks of anaemia, relative ventricular mass(rMV) in warm-acclimated rainbow trout had already increased significantly and, by the eighth week of anaemia,rMV was 58% greater than in the sham-injected control fish. Temperature modulated the anaemia-induced ventricular remodelling and erythropoietic responses, as indicated by cold-acclimation reducing the extent of the cardiac remodelling and slowing erythropoietic recovery. For example,in cold-acclimated fish, PHZ reduced Hct to 8.8±1.9% (ranging from 4–16%) and increased rMV by 15% over a 4-week period, whereas the same treatment in warm-acclimated fish reduced Hct to only 17.4±2.1% (ranging from 6–29%) and yet increased rMV by 28%. Cold-acclimated fish also recovered more slowly from anaemia. In addition, warm-acclimated fish maintained compact myocardium between 32% and 37% during anaemia, while cold-acclimated fish responded with an increase in compact myocardium (from 29% to 37%). Routine cardiac output (Q̇) was continuously monitored following a single PHZ injection to examine the initial cardiac response to anaemia. Contrary to expectations, acute anaemia did not produce an immediate, proportionate increase in routine Q̇. In fact, Q̇ did not increase significantly until Hct had decreased to 10%, suggesting that rainbow trout may initially rely on venous oxygen stores to compensate for a reduced arterial oxygen-carrying capacity. Thus, we conclude that myocardial oxygenation, acclimation temperature and cardiac work load could all influence anaemia-induced cardiac remodelling in rainbow trout.
Collapse
Affiliation(s)
- Danielle L Simonot
- Department of Biological Sciences, 8888 University Drive, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada
| | | |
Collapse
|
49
|
Farrell AP, Axelsson M, Altimiras J, Sandblom E, Claireaux G. Maximum cardiac performance and adrenergic sensitivity of the sea bassDicentrarchus labraxat high temperatures. J Exp Biol 2007; 210:1216-24. [PMID: 17371920 DOI: 10.1242/jeb.002881] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We examined maximum cardiac performance of sea bass Dicentrarchus labrax acclimated to 18°C and 22°C, temperatures near the optimum for growth of this species. Our aim was to study whether cardiac performance,especially the effect of adrenergic stimulation, differed when compared to salmonids. Sea bass and salmonids are both athletic swimmers but their cardiac anatomy differs markedly. The sea bass ventricle does not receive any oxygenated blood via a coronary circulation while salmonids have a well-developed arterial supply of oxygen to the compact layer of the ventricle. Using in situ perfused heart preparations, maximum cardiac performance of 18°C-acclimated sea bass (i.e. cardiac output=90.8±6.6 ml min–1 kg–1 and power output=11.41±0.83 mW g–1) was found to be comparable to that previously reported for rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta at similar temperatures and with tonic adrenergic (5 nmol l–1 adrenaline) stimulation. For 22°C-acclimated sea bass, heart rate was significantly higher, but maximum stroke volume was reduced by 22% (1.05±0.05 ml kg–1)compared with 18°C (1.38± 0.11 ml kg–1). As a result, maximum cardiac output (99.4±3.9 ml min–1kg–1) was not significantly different at 22°C. Instead,maximum power output was 27% higher at 22°C (14.95±0.96 mW g–1) compared with 18°C, primarily because of the smaller relative ventricular mass in 22°C-acclimated sea bass. Compared with tonic adrenergic stimulation with 5 nmol l–1 adrenaline, maximum adrenergic stimulation of the sea bass heart produced only modest stimulatory effects at both temperatures (12–13% and 14–15% increases in maximum cardiac output and power output, respectively, with no chronotropic effect). Adrenergic stimulation also increased the cardiac sensitivity to filling pressure, with the maximum left-shift in the Starling curve being produced by 50–100 nmol l–1 adrenaline at 18°C and 10–50 nmol l–1 adrenaline at 22°C. We show that the sea bass, which lacks a coronary arterial oxygen supply to the ventricle, has a powerful heart. Its maximum performance is comparable to a salmonid heart,as is the modest stimulatory effect of adrenaline at high temperature.
Collapse
Affiliation(s)
- Anthony P Farrell
- UBC Centre for Aquaculture and the Environment, Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
| | | | | | | | | |
Collapse
|
50
|
Stecyk JAW, Farrell AP. Effects of extracellular changes on spontaneous heart rate of normoxia-and anoxia-acclimated turtles (Trachemys scripta). J Exp Biol 2007; 210:421-31. [PMID: 17234611 DOI: 10.1242/jeb.02653] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYHeart rate (fH) of the anoxia-tolerant freshwater turtle (Trachemys scripta) during prolonged anoxia exposure is 2.5-to 5-times lower than the normoxic rate, but whether alterations in blood composition that accompany prolonged anoxia contribute to this bradycardia is unknown. We examined how temperature acclimation, oxygen deprivation,acidosis, hyperkalemia, hypercalcemia and adrenaline affect chronotropy in the turtle myocardium. We monitored spontaneous contraction rates of right-atrial preparations obtained from 21°C- and 5°C-acclimated turtles that had been exposed to either normoxia or anoxia (6 h at 21°C; 2 weeks at 5°C). Sequential exposures to saline solutions were designed to mimic, in a step-wise manner, the shift from a normoxic to anoxic extracellular condition (for normoxia-acclimated preparations) or the reverse (for anoxia-acclimated preparations). Our results clearly show that prolonged anoxia exposure re-sets the intrinsic fH of turtles at both temperatures, with reductions in intrinsic fH in the range of 25%–53% compared with normoxia. This intrinsic change would contribute to the bradycardia observed with prolonged anoxia. Further, we found negative chronotropic effects of extracellular anoxia, acidosis and hyperkalemia, and positive chronotropic effects of hypercalcemia and adrenaline. The exact nature of these extracellular effects depended, however,on the acclimation temperature and the prior exposure of the animal to anoxia. With normoxia-acclimated preparations at 21°C, combined anoxia and acidosis (pH reduced from ∼7.8 to ∼7.2) significantly reduced spontaneous fH by 22% and subsequent exposure to hyperkalemia (3.5 mmol l–1K+) further decreased fH. These negative chronotropic effects were ameliorated by increasing the adrenaline concentration from the tonic level of 1 nmol l–1 to 60 nmol l–1. However, in anoxia-acclimated preparations at 21°C, anoxia alone inhibited fH (by ∼30%). This negative chronotropic effect was counteracted by both hypercalcemia (6 mmol l–1Ca2+) and adrenaline (60 nmol l–1). At 5°C,only the combination of anoxia, acidosis (pH reduced from ∼8.0 to∼7.5) and hyperkalemia (3.5 mmol l–1 K+)significantly reduced spontaneous fH (by 23%) with preparations from normoxia-acclimated turtles. This negative chronotropic effect was fully reversed by hypercalcemia (10 mmol l–1Ca2+). By contrast, spontaneous fH of anoxia-acclimated preparations at 5°C was not affected by any of the extracellular changes. We conclude that prior temperature and anoxia experiences are central to determining fH during prolonged anoxia in Trachemys scripta both as a result of the re-setting of pacemaker rhythm and through the potential influence of extracellular changes.
Collapse
Affiliation(s)
- Jonathan A W Stecyk
- Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
| | | |
Collapse
|