[Effect of propranolol on ouabain-sensitive Na+,K+-ATPase activity of the rat heat]

Effect of propranolol on activity of basal ATP-ase measured in presence of Mg2+ activator, on that of total ATP-ase determined in presence of Mg2+, Na+, K+ activators and on that of Na+,K+-activated ATP-ase calculated from the difference of the previous two ones has been studied. Propranolol has not considerably influenced basal ATP-ase activity in 10(-7)-10(-4) M concentrations, 30-50% inhibition has been found in 1 X 10(-3)-5 X 10(-3) M concentrations. Effect of propranolol on total ATP-ase activity has been found to be dependent on doses and inhibition has been greater than inhibition experienced in case of basal ATP-ase. Enzyme kinetic investigations have shown that in case of basal ATP-ase propranolol has only decreased affinity to substrate but has not influenced rate of enzyme reaction, in case of total ATP-ase the affinity to the substrate has not changed but the reaction rate has significantly decreased. Ineffective concentrations of propranolol have potentiated inhibition effect of Na+,K+-ATP-ase. The authors have supposed that the observed changes have been results of non-specific membrane effects of propranolol and composition of membrane lipids may also play an important role.