[Changes in the activity and regulatory properties of Na, K-ATPase from the myocardial sarcolemma in total graded ischemia].

Na, K-ATPase activity of the rat and guinea-pig myocardial sarcolemma and its sensitivity to digoxin (DG) and carbamylcholine (CCh) were investigated during experimental ischemia. Ischemia was induced by the incubation of hearts in the air at 37 degrees C. This 15-, 30- and 45-min treatment led to a decrease in enzymatic activity which was similar in both animal species. Dose-related dependence of DG effect (10(-8)-10(-2) M) on sarcolemmal Na, K-ATPase activity of guinea-pig ischemic hearts did not differ from the control, whereas the rat enzyme sensitivity to glycosides rose with the progress of ischemia. CCh (10(-7)-10(-3) M) produced an inhibition of Na, K-ATPase activity which had reached 40% both in the rat and guinea-pig myocardial preparations. This effect was blocked by atropine (10(-6) M). The magnitude of enzyme responses to CCh declined depending on the duration of ischemia, with it being greater in guinea-pig sarcolemma than in rat membrane. The increased sensitivity of the rat Na, K-ATPase to CCh was also observed.