Energy metabolism and ion fluxes across cardiac membranes.

The possible role of the intracellular creatine kinase system in energy transport and in the metabolic control of ion fluxes across the cardiac cell membranes has been studied. The experimental data reported indicate that creatine kinases bound to the sarcolemmal membrane and to the membrane of sarcoplasmic reticulum are coupled to Na+, K+-ATPase and Ca2+-ATPase, respectively, and ensure rapid rephosphorylation of ADP produced in the ATPase reactions, maintaining a high and constant ATP:ADP ratio near the active centers of ATPases. The ability of creatine phosphate to increase the rate of activator calcium entry across the surface membrane into cardiac cells has been experimentally demonstrated. It is concluded that the intracellular creatine kinase system can exert metabolic control of heart muscle contraction.