Vasorelaxant Effect of 17 alpha-Ethynylestradiol on Human Saphenous Vein

Abstract

Purpose: A protective effect for estrogens against cardiovascular problems has long been known. The aim of this study was to investigate the vasorelaxant effect of 17 alpha-Ethynylestradiol (17 alpha-EE) on human saphenous vein. Methods: 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 degrees C and gassed with carbogen under 3gr optimum tension. The effect of different concentrations of 17 alpha-EE (2-40 mu M) on vascular tone was investigated in veins precontracted with PGF(2 alpha). 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 17 alpha-EE were directly compared to those obtained in the same tissues in the absence of the inhibitors. Results: The mean relaxations induced by 17 alpha-EE with concentrations of 2, 5, 10, 20 and 40 mu M in tissues precontracted with PGF(2 alpha) were 19.8 +/- 5.5%, 26.1 +/- 10.8%, 32.2 +/- 7.4%, 48.6 +/- 10.8% and 56 +/- 7.6%, respectively. The results of the inhibition of potassium channels, nitric oxide synthase, guanylylcyclase, cyclooxygenase and removing endothelium in relaxation induced by 17 alpha-EE on precontracted veins with PGF(2 alpha) proved no significant differences. Conclusion: This study showed that 17 alpha-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.