Stimulation of Vascular Smooth Muscle Sodium, Potassium--Adenosinetriphosphatase by Vasodilators

Abstract

A ouabain-sensitive, Mg²⁺-dependent, Na⁺, K⁺-stimulated adenosinetriphosphatase (ATPase) isolated from canine mesenteric arteries was activated by the following vasodilators: hydralazine, diazoxide, PGE₁, PGE₂, PGA₂, and minoxidil. Epinephrine, norepinephrine, and isoproterenol also stimulated the ATPase, but PGF_2α was ineffective. Since these vasodilators activate the adenylate cyclase of vascular smooth muscle, the effects of cyclic adenosine monophosphate (AMP) and theophylline on the Na⁺, K⁺-ATPase were studied; both substances caused a concentration-dependent increase in enzymatic activity. Propranolol blocked the catecholamine-induced stimulation of Na⁺, K⁺-ATPase, and polyphloretin phosphate antagonized the effects of the prostaglandins. It is concluded that vasodilatation in response to these substances is associated with the stimulation of the Na⁺, K⁺-ATPase of vascular smooth muscle probably mediated through cyclic AMP.