Comparative Aspects of Hypoxia Tolerance of the Ectothermic Vertebrate Heart

Gesser, H.; Overgaard, Johannes

doi:10.1007/978-3-540-93985-6_12

Cited by 2 publications

(3 citation statements)

References 92 publications

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“…An additive effect of acidosis during severe hypoxia exposure was evident in the significant decreases in maximum cardiac performance (Q max and PO max ) as well as in f H . In most fishes, the additive and negative inotropic effects of acidosis (Farrell et al, 1983;Driedzic and Gesser, 1994;Gesser and Overgaard, 2009) markedly decrease cardiac twitch force and in situ cardiac performance (Poupa et al, 1978;Gesser and Poupa, 1983;Overgaard et al, 2005). In our study, acidosis diminished the increases in cardiac V S and Q when P in was increased (Fig.3B).…”

Section: Effects Of Severe Hypoxia On Maximum Cardiac Performance Andsupporting

confidence: 52%

“…With the in situ perfused heart preparation, the accumulation of lactate and H + from glycolysis normally seen in plasma does not occur with severe hypoxia in vivo. Therefore, in order to simulate the negative effects of acidosis on cardiac contractility, which occurs via decreased sensitivity of the myofilament to Ca 2+ as well as the depressive effect of acidosis on the pacemaker (Orchard and Kentish, 1990;Crampin and Smith, 2006;Gesser and Overgaard, 2009), we examined the additional effect of low pH (7.25) during severe hypoxia. An additive effect of acidosis during severe hypoxia exposure was evident in the significant decreases in maximum cardiac performance (Q max and PO max ) as well as in f H .…”

Section: Effects Of Severe Hypoxia On Maximum Cardiac Performance Andmentioning

confidence: 99%

“…Two mechanisms have emerged for achieving a cardiac ATP demand below the MGP during anoxia: (1) exhibiting a naturally low routine cardiac ATP demand that can be sustained by anaerobic glycolysis [e.g. hagfish and crucian carp (Farrell and Stecyk, 2007;Gesser and Overgaard, 2009)] or (2) substantially downregulating cardiac ATP demand to a level sustainable by anaerobic glycolysis [e.g. painted turtle and common carp (Cyprinus carpio) (Jackson, 2002;Stecyk and Farrell, 2006)].…”

Section: Introductionmentioning

confidence: 99%

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Exceptional cardiac anoxia tolerance in tilapia (Oreochromis hybrid)

Lague¹,

Speers‐Roesch

Richards

et al. 2012

Journal of Experimental Biology

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SUMMARYAnoxic 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 heartʼs MGP. The MGP of the ectothermic vertebrate heart has previously been suggested to be ~70nmol ATPs -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 , 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.

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Section: Effects Of Severe Hypoxia On Maximum Cardiac Performance Andsupporting

confidence: 52%

Section: Effects Of Severe Hypoxia On Maximum Cardiac Performance Andmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Exceptional cardiac anoxia tolerance in tilapia (Oreochromis hybrid)

Lague¹,

Speers‐Roesch

Richards

et al. 2012

Journal of Experimental Biology

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The Effect of Developmental Hypoxia on Cardiac Physiology in Three Species: Alligator mississippiensis, Chelydra serpentina, and Danio rerio

Smith

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In this dissertation, I explored the effects of developmental hypoxia on heart contractility in three separate species of ectotherms: the common snapping turtle (Chelydra serpentina), the American alligator (Alligator mississippiensis), and the zebrafish (Danio rerio). I began with the common snapping turtle and tested whether the utilization of the sarcoplasmic reticulum was altered in response to developmental hypoxia. In the next two chapters, developmental hypoxia of the American alligator was explored studying how the cardiac tissue was affected, specifically in physiological stressors, sarcoplasmic reticulum utilization and sensitivity to pharmacological increases in contractility. The last chapter explored how zebrafish heart contractility was altered in response to chronic hypoxia from egg to adult. Findings from these chapters suggest that while developmental hypoxia did alter cardiac contractility, it did not alter the response of the heart to physiological stressors such as increased heart rate or under hypoxia. Overall, these findings contribute to increasing the current understanding of how developmental hypoxia alters the cardiovascular system but with an emphasis on the cardiac tissue level.

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Comparative Aspects of Hypoxia Tolerance of the Ectothermic Vertebrate Heart

Cited by 2 publications

References 92 publications

Exceptional cardiac anoxia tolerance in tilapia (Oreochromis hybrid)

Exceptional cardiac anoxia tolerance in tilapia (Oreochromis hybrid)

The Effect of Developmental Hypoxia on Cardiac Physiology in Three Species: Alligator mississippiensis, Chelydra serpentina, and Danio rerio

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