Abstract

The effect of substrates on potassium contracture tension of the isolated rat ventricle strip was investigated. The contracture tension magnitude of ventricle strips exposed to potassium rich medium was markedly greater with medium containing pyruvate or acetate than with glucose as the substrate. The effect of substrates on contracture tension was not related to their ability to maintain the ATP stores of the heart, for there was not a significant difference in the ATP levels in ventricle strips incubated in medium containing pyruvate, pyruvate + glucose, or glucose. Glucose reduced the K-contracture tension magnitude of heart strips suspended in medium containing pyruvate or acetate as substrate; 3-0-methylglucose and 2-deoxy-D-glucose did not have this action on K-contracture tension. The reduction of K-contracture tension by glucose was inhibited by iodoacetate and fluoride. Under anaerobic conditions, 50 mM glucose significantly reduced the K-contracture tension of ventricle strips suspended in pyruvate medium. The findings of this study suggest that glucose metabolism has an action on K-contracture tension in cardiac muscle that is not shared by acetate or pyruvate.

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