Abstract

The effect of substrates on the positive inotropic action of malonate on electrically stimulated rat ventricle strips was investigated. Malonate exerted a marked positive inotropic effect in substrate-free and glucose-containing media, but not when pyruvate was employed as a substrate. The positive inotropic action of malonate was inhibited by iodoacetate. The magnitude and time course of the positive inotropic effect of malonate was similar to the positive inotropic action of pyruvate. A working hypothesis for the mechanism of the positive inotropic action of malonate is that malonate by an action on the Embden-Meyerhof pathway eliminates a rate limiting step in the conversion of glycogen and glucose to pyruvate.