Vasorelaxant Effect of 17α-Ethynylestradiol on Human Saphenous Vein

A protective effect for estrogens against cardiovascular problems has long been known. The aim of this study was to investigate the vasorelaxant effect of 17α Ethynylestradiol (17α-EE) on human saphenous vein. The veins were suspended horizontally between two triangular stainless steel hooks for the measurement of isometric tension in individual organ baths containing 10ml Krebs solution, at 37°C and gassed with carbogen under 3gr optimum tension. The effect of different concentrations of 17α-EE (2-40 μM) on vascular tone was investigated in veins precontracted with PGF2α. Relaxation was measured after 40min and expressed as the percent decrease of initial contraction. To determine the involvement of potassium channels, endothelium, nitric oxide synthase, guanylylcyclase and prostaglandins in the vasorelaxant effect of estrogen, the veins were incubated with tetraethyl ammonium, N-nitro-L-arginine methyl ester, methylene blue or indomethacin, respectively for 20min prior to experimentation. Responses to 17α-EE were directly compared to those obtained in the same tissues in the absence of the inhibitors. The mean relaxations induced by 17α-EE with concentrations of 2, 5, 10, 20 and 40μM in tissues precontracted with PGF2α were 19.8 ±5.5%, 26.1±10.8%, 32.2±7.4%, 48.6±10.8%and56±7.6%, respectively. The results of the inhibition of potassium channels, nitric oxide synthase, guanylylcyclase, cyclooxygenase and removing endothelium in relaxation induced by 17α-EE on precontracted veins with PGF2α proved no significant differences. This study showed that 17α-EE has significant vasorelaxant effect on human saphenous vein in a concentration-dependent manner. This effect is probably independent of potassium channels, nitric oxide synthase, guanylylcyclase, prostaglandin synthesis and endothelium functions.