[Animal experiments on the effect of triamterene and amiloride on heart and circulation and the toxicity of digoxin (author's transl)].

1. In anesthetized cats 2,4,7-triamino-6-phenyl-pteridine (triamterene) (5 mg/kg i.v.) causes a short-lasting increase in blood pressure, a decrease in heart rate, whereas the contractility (see article) remains unchanged. N-Amidino-3,5-diamino-6-chloropyrazinecarboxamide (amiloride) (5 mg/kg i.v.) causes a fall of blood pressure, an increase in heart rate, and an increase in contractility. 2. In cats the i.v. toxicity of digoxin is diminished by pretreatment with triamterene or amiloride; the arrhythmias and the cardiac arrest are significantly delayed in the course of an infusion of digoxin. In guinea-pigs a pretreatment with triamterene only delays the arrhythmias but not the lethal effect of digoxin or g-strophanthin. 3. In the isolated atria of the guinea-pig triamterene and amiloride (5 mug or 50 mug/ml) lowers the rate of contraction and prolongs the functional refractory period. The force of contraction is increased by triamterene and diminished by amiloride.