Influence of triamterene and hydroxytriamterene sulfuric acid ester on diuresis and saluresis in rats after oral and intravenous application.

Previous transport measurements on the submaxillary duct of the rat, the model epithelium for the distal nephron, showed that even the phase-II metabolite of triamterene (TA), hydroxytriamterene sulfuric acid ester (OH-TA-ester), has a diuretic effect. The present studies were aimed at answering the question whether or not this finding was also valid in vivo. Clearance measurements in the rat after i.v. injection of OH-TA-ester did result in an increased diuresis and natriuresis. In comparison with the native triamterene the phase -II metabolite caused only a relative potassium retention. The ester was inactive when administered orally. The potassium loss after administration of furosemide could be prevented by simultaneous i.v. administration of the OH-TA-ester.