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Regulation of metabolic energy supply and demand of the heart during hypoxia exposure in tilapia

Journal article
Authors B. Speers-Roesch
Erik Sandblom
G.Y. Lau
A.P. Farrell
J.G. Richards
Published in American Journal of Physiology: Regulatory, Integrative and Comparative Physiology
Volume 298
Issue 1
Pages R104 - R119
ISSN 1522-1490
Publication year 2010
Published at Department of Zoology
Pages R104 - R119
Language en
Links dx.doi.org/10.1152/ajpregu.00418.20...
Subject categories Animal physiology

Abstract

The ability of an animal to depress ATP turnover while maintaining metabolic energy balance is important for survival during hypoxia. In the present study, we investigated the responses of cardiac energy metabolism and performance in the hypoxia-tolerant tilapia (Oreochromis hybrid sp.) during exposure to environmental hypoxia. Exposure to graded hypoxia (≥92% to 2.5% air saturation over 3.6±0.2 h) followed by exposure to 5% air saturation for 8 h caused a depression of whole animal oxygen consumption rate that was accompanied by parallel decreases in heart rate, cardiac output, and cardiac power output (CPO, analogous to ATP demand of the heart). These cardiac parameters remained depressed by 50-60% compared with normoxic values throughout the 8 h exposure. During a 24 h exposure to 5% air saturation, cardiac [ATP] was unchanged compared with normoxia and anaerobic glycolysis contributed to ATP supply as evidenced by considerable accumulation of lactate in the heart and plasma. Reductions in the provision of aerobic substrates were apparent from a large and rapid (in <1 h) decrease in plasma [non-esterified fatty acids] and a modest decrease in activity of pyruvate dehydrogenase (PDH). Depression of cardiac ATP demand via bradycardia and an associated decrease in CPO appears to be an integral component of hypoxia-induced metabolic rate depression in tilapia and likely contributes to hypoxic survival.

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