Abstract
Direct effect of cyclic AMP (c-AMP) on myocardial contractility was investigated in the isolated canine heart muscle. c-AMP at a concentration of 3.3×10-4M produced a decrease in isometric peak force to 75.8% of the control on the average. The result suggests a difference on the effect of exogenous c-AIVLP from that of endogenous one on the contractile behavior of the heart muscle.