Mode of action of cyclothiazide and triamterene. Ex vivo effect on 22Na and 86Rb efflux from arterial smooth muscle.

Acute oral cyclothiazide treatment of conscious rats increased ex vivo 86Rb efflux from tail artery smooth muscle. This effect was blocked by oral triamterene. Identical results were obtained in binephrectomized rats, suggesting that the two drugs had a direct effect on smooth muscle K+ (86Rb) permeability. Decreased ex vivo smooth muscle 22Na efflux induced by oral cyclothiazide and triamterene is probably secondary to their renal actions, since there was no effect in binephrectomized rats.