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Abstract

This study was designed to compare vasorelaxant effects of the sildenafil and verapamil on isolated rat aorta. Endothelium intact and denuded aortic rings were suspended in organ chambers. Sildenafil (10-10 to 10-4 M) induced a dose-dependent vasodilation of phenylephrine precontracted aortic rings. Relaxation of endothelium intact and denuded aortic rings caused by 10-4 M sildenafil was about 96 and 79%, respectively. Verapamil (10-10 to 10-4 M) induced a dose-dependent vasodilation of phenylephrine precontracted aortic rings. Relaxation of endothelium intact and denuded aortic rings caused by 10-4 M verapamil was about 99 and 98%, respectively. In the phenylephrine precontracted aortic rings, pD2 values for sildenafil were 4.93±0.59 and 4.11±0.62 in the presence and absence of endothelium, respectively. The pD2 values for verapamil were not different in the presence and absence of endothelium (5.15±1.05 vs 4.96±1.14). Verapamil and sildenafil showed a similar degree of vasorelaxant effect in the intact aortic rings, although there was a significant difference in the degree of relaxation in the absence of endothelium (98 vs 79%). Sildenafil induced both endothelium-dependent and independent vasorelaxation on the aortic rings. Although, there was no significant difference in the degree of relaxation induced by verapamil and sildenafil in aortic rings with intact endothelium, verapamil has more relaxing effect in the denuded aortic rings.