Reversibility of the effect of digitoxin, strophanthidine and strophanthidine-3-bromoacetate on the papillary muscle and a microsomal Na+-K+-activated ATPase of the guinea pig

Abstract

The reversibility of the inhibitory action of strophanthidin, strophanthidin-3-bromoacetate, and digitoxin on the Na+-K+-ATPase activity (microsomal fraction, guinea-pig brain) was compared with the rate of decline of their positive inotropic effects (papillary muscle, guinea-pig heart) after exposure to drug-free solution. The actions of strophanthidin and digitoxin were easily reduced on both systems. Strophanthidin-3-bromoacetate, however, was found to have an irreversible blocking effect on the transport ATPase, whereas its inotropic action could be rapidly abolished.