Effects of acebutolol, practolol and propranolol on the rat heart sarcolemma

Abstract

The actions of acebutolol, practolol and propranolol on the rat heart sarcolemmal ATPase, adenylate cyclase and calcium binding activities were studied. None of these agents had any effect on the basal adenylate cyclase activity. Only propranolol at 2 mM or higher concentrations depressed calcium binding; this inhibitory effect was less pronounced at high concentrations of calcium. Propranolol (1–5 mM), but not practolol, markedly depressed Na +-K + ATPase activity whereas acebutolol (3–5 mM) produced a slight but significant inhibition. Propranolol (1–5 mM), but not acebutolol or practolol, also inhibited the Ca 2+ ATPase and Mg 2+ ATPase activities. These results indicate sarcolemmal membrane as the site affected by propranolol and it is suggested that the cardiodepressant action of high doses of this agent may partly be due to changes in the sarcolemmal ATPase and calcium binding activities.