Influence of myocardial isomyosins on cardiac performance and oxygen consumption

Abstract

There was 21% isomyosin V 1 in the 12 month SHR (Spontaneous Hypertensive Rat) and 70% isomyosin V 1 in the 6 month WKY (Wystar-Kyoto), nevertheless there was no difference in maximum developed pressure nor maximum dP dt in the isovolumically beating hearts of the two sets of animals. [Hearts were perfused with hypercalcemic perfusate in the presence of isoproterenol (10 −7M)]. There was, however, a a 32% reduction in oxygen consumption per gram of dry weight per beat in the 12 month SHR as compared to the 6 mo WKY. Associated with a shift towards isomyosins V 2 and V 3 in the 6 and 12 month WKY and SHR there was no corresponding change in maximum dP dt nor developed pressure, but there was a conservation in oxygen consumption.