[Effects of cilostazol, a cyclic AMP phosphodiesterase inhibitor, on pulmonary vascular tone].

We examined the effect of Cilostazol, a cyclic AMP phosphodiesterase inhibitor, rat isolated pulmonary arterial ring tone. Cilostazol dilated pulmonary arterial rings pre-contracted with 10(-6) M phenylephrine in a dose-dependent manner (ED50 3.00 x 10(-6) M). This vasodilatory effect of Cilostazol was not affected by pretreatment with meclofenamate (10(-5) M), mechanical endothelium denudation, methylene blue (10(-5) M) or nitro-L-arginine (2 x 10(-4) M). The vasodilatory effect of Cilostazol on rat thoracic aortic rings was stronger than that on rat pulmonary arterial ring (ED50 1.89 x 10(-6) M). Cilostazol (10(-6) M-10(-4) M) inhibited hypoxic contraction of rat pulmonary rings in a dose-dependent manner. Our experimental data indicated that Cilostazol caused vasodilation regardless of vascular endothelium function and inhibited hypoxic contraction due to inhibition of cyclic AMP phosphodiesterase.