Ethacrynic acid induced inotropism

Abstract

Ethacrynic acid (ECA), a sulfhydryl group inhibiting diuretic was examined for positive inotropic effects. These were found to be present in isolated guinea pig left atria studied in 0.9 and 1.8 mM Ca bathing solutions and were partially dependent upon adrenergic mechanisms (presumably secondary to norepinephrine release from sympathetic nerve endings) and partly independent of such mechanisms as demonstrated by propranolol induced beta-blockade and reserpine-induced catecholamine depletion. The mechanism of the non-beta adrenergic inotropism is unclear but may relate to the ability of ECA to inhibit the sarcolemmal Na-K-Mg-dependent ATPase. ECA-induced premature contractile failure occurred in all atria as well as a late increase in diastolic tension, the latter being comparable to that described for toxic doses of cardiac glycosides in similar preparations.