GENDER DIFFERENCE IN IMPROVEMENT OF ENDOTHELIUM-DEPENDENT VASODILATION AFTER ESTROGEN SUPPLEMENTATION

Objectives. We examined whether there is a gender difference in the im provement of endothelium-dependent vasodilation after estrogen supplem entation. Background. Estrogen therapy reduces the risk of cardiovascu lar events in postmenopausal women, and the augmented release of endot helium derived nitric oxide (NO) by estrogens has been suggested to be one of the mechanisms for the cardioprotective effects of estrogen. M ethods. With ultrasound technique, we measured the diameter and blood flow of the brachial artery at rest, during reactive hyperemia after t ransient occlusion and after nitroglycerin administration before and a fter estradiol supplementation in 15 postmenopausal women (mean 63 yea rs) and in 15 men matched for age and risk factors for atherosclerosis . Results. Estradiol supplementation augmented the flow-mediated vasod ilation and serum level of nitrite/nitrate (metabolites of NO) in wome n (respectively, from a mean +/- SEM of 8.0 +/- 0.6% to 12.9 +/- 0.6% [p < 0.01 by analysis of variance (ANOVA)] and from 64.9 +/- 8.7 to 93 .7 +/- 9.4 mu mol/liter [p < 0.05 by ANOVA]) but not in men (respectiv ely, from 8.1 +/- 0.6% to 8.3 +/- 0.7% and from 57.8 +/- 6.7 to 60.8 /- 5.4 mu mol/liter). The increases in blood flow during reactive hype remia and in diameter after nitroglycerin administration were not affe cted by estradiol supplementation in either men or women. Conclusions. Estradiol supplementation improves endothelium-dependent vasodilation in women, probably because of augmented NO production/release, but no t in men. Thus, there may be gender differences in the effects of estr ogen therapy on endothelial functions and NO production/release. (C) 1 997 by the American College of Cardiology.