Effect of ethacrynic acid on spontaneous contractions of isolated guinea-pig atria

Abstract The effect of different doses of ethacrynic acid (EA), 25–200 μg/ml, has been studied on the rate and force of contractions of isolated guinea-pig atria. It has been shown that EA produces dose-dependent increases in force of contraction (31–72%) and of rate (13–36%). Pretreatment of guinea pigs with reserpine, 5 mg/kg or of the isolated atria with propranolol (2 μg/ml) inhibited the inotropic and chronotropic effects of EA. Pretreatment of the atria with cocaine (5 μg/ml) inhibited the inotropic effect of EA, but had no significant effect on its chronotropic action. It is concluded that in guinea-pig atria, the positive inotropic and chronotropic action of EA, is probably due to the release of endogenous catecholamines.