Vasorelaxant Effect of Sildenafil on Aorta and Pulmonary Artery in Rabbits

Abstract

This in vitro study was designed to determine the direct vasorelaxant effect of the sildenafil on isolated rabbit pulmonary artery and compare it with the response of isolated rabbit aorta. Endothelium intact aortic and pulmonary artery rings from seven domestic rabbits were suspended in organ chambers containing 15 mL Krebs solution aerated with 95% O2, 5% CO2. In both phenylephrine and potassium chloride (KCl) precontracted vessels, relaxant responses of sildenafil were recorded by strain gauge transducers connected to a polygraph. Sildenafil (10-9 to 3×10-5 M) induced a dose-dependent vasodilation of phenylephrine precontracted aorta and pulmonary artery; 55 and 95% relaxations were obtained, respectively, at a concentration of 3×10-5 M. Sildenafil also caused a dose-dependent vasodilation of KCl-precontracted aorta and pulmonary artery, but this vasodilation was significantly lesser. Sildenafil-induced relaxations were higher in pulmonary arteries when compared to aortic rings precontracted with either phenylephrine or KCl. We concluded that sildenafil induces a dose-dependent vasodilation on phenylephrine and KCl-precontracted rabbit aorta and pulmonary artery. This vasodilatory effect is more potent in pulmonary arteries than in aortic rings. © 2006 Asian Network for Scientific Information.