[Inhibition of the exchange of Na+ for K+ and and H+ by triamterene (in epithelia)(author's transl)]

Abstract

The salivary duct epithelium, which actively transports Na+, K+ and H+/HCO3/- similarly to renal distal tubules, was used as a model tissue to study the mechanism of action of triamterene (Jatropus, Dyrenium) on electrolyte transport. Triamterene was only effective when administered from the luminal side of the duct, not from the interstitial side. 10-4 M triamterene completely blocked Na+-reabsorption. At the same time K+ secretion dropped to half of control, whereas HCO-/3 accumulated in the duct lumen following reduced H+ secretion. These changes in electrolyte transport are caused by an inhibition of Na+-entry by triamterene as suggested by measurements of ion permeability of the cell membrane. Triamterene has no specific effect on the membrane-bound ATPase. Since Na+-entry is functionally coupled with exit of K+ and H+ from cell to lumen, impairment of Na+-entry by triamterene necessarily causes reduction of K+ and H+ secretion into lumen.