Oxidation of Carbon14-Labeled Glucose, Pyruvate and Succinate by Isolated Contracting Myocardium

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Abstract
Oxidation of C14-labeled glucose, pyruvate and succinate at ph 6.2 and 7.4 by isolated contracting and resting rat ventricular strips which had become hypodynamic after prolonged contraction in substrate-free medium was studied; in addition, the effects of these substrates upon the force of contraction of the strips were investigated. The inability of succinate at ph 7.4 and of glucose at ph 6.2 to maintain contractile activity was found to be associated with failure of these substances to be oxidized at appreciably greater rates by contracting than by resting muscle. However, substantial recovery together with greater utilization by contracting than resting strips occurred with succinate at ph 6.2 and glucose at ph 7.4. On the other hand, the oxidation of pyruvate and its effect upon the force of contraction of the myocardium were not significantly different at these two ph values; in both cases substantial recovery of activity together with an increased rate of oxidation by contracting strips occurred.