Study of possible mechanism of protective effect of phosphocreatine on ischemic myocardium

The accumulation of (/sup 32/P)phosphocreatine by control and isolated perfused ischemic rat hearts was studied. It was found that at phosphocreatine concentrations of 0.5-10 mM in the perfusing solution the rate of phosphocreatine accumulation was twice as high in hearts subjected to ischemia for 35 min as in the control hearts and constituted 182 nmoles/min/g dry weight tissue at a phosphocreatine concentrations in the perfusate of 10 mM. 5'-Nucleotidase and phosphatase activities were found in the crude plasma membrane fraction from rat hearts. The pH-dependence of the activity of these enzymes was studied. The 5'-nucleotidase activity decreased 4- to 5-fold with a drop in the pH from 8.0 to 6.0. The phosphatase activity of the preparations increased 2-fold with a drop in the pH from 8.0 to 6.0. The 5'-nucleotidase activity was inhibited by 10 mM phosphocreatine in the presence of 5 mM Mg/sup 2 +/, and the degree of the inhibition depended on the pH. Maximum inhibition by phosphocreatine (58%) was observed at pH 6.0. The inhibition of phosphatase by phosphocreatine did not depend on the pH and reached 20% in the presence of 10 mM phosphocreatine. Some possible mechanisms of the protective effect of phosphocreatine on an ischemicmore » myocardium are discussed.« less