| Summary: | Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. Biology Includes bibliographical references Cardiac muscle from anoxia tolerant and intolerant fishes was used to investigate the importance of ATP-sensitive potassium channels (Katp) in the control of anaerobic cardiac function. KArp channels contribute to anaerobic cardioprotection in mammals yet little is known of their action in more hypoxia tolerant animals. Isometrically contracting ventricular muscle preparations were used to study sarcolemmal and mitochondrial Katp channel activity in the myocardium of three species of teleost fishes (Lipossarcus pardalis'm Limanda ferruginea. and Gadus morhua) with varying cardiac hypoxia tolerances. Channel activity was assessed pharmacologically using the non-specific K.\tp channel blocker glibenclamide, the mitochondrial specific blocker 5-hydroxydecanoic acid and the agonist, diazoxide to determine the involvment of KArp channels in anaerobic cardiac performance. Results suggest that cardiac Kaip channels from hypoxia tolerant fishes are tonically active, resulting in a constant cardioprotection similar to the "preconditioned" state which can be induced by various methods in mammalian hearts. These studies clearly show that Kaip channels are important for anaerobic cardiac function in anoxia tolerant fish.
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