Influence of ischemia-reperfusion injury on endothelial function in men and women with similar serum estradiol concentrations

Prior data suggest that, relative to the early follicular phase, women in the late follicular phase are protected against endothelial ischemia-reperfusion (I/R) injury when estradiol concentrations are highest. In addition, endothelial I/R injury is consistently observed in men with naturally low endogenous estradiol concentrations that are similar to those of women in the early follicular phase. Therefore, the purpose of this study was to determine whether the vasodeleterious effect of I/R injury differs between women in the early follicular phase of the menstrual cycle and age-matched men. We tested the hypothesis that I/R injury would attenuate endothelium-dependent vasodilation to the same extent in women and age-matched men with similar circulating estradiol concentrations. Endothelium-dependent vasodilation was assessed via brachial artery flow-mediated dilation (duplex ultrasound) in young healthy men (n = 22) and women (n = 12) before (pre-I/R) and immediately after (post-I/R) I/R injury, which was induced via 20 min of arm circulatory arrest followed by 20-min reperfusion. Serum estradiol concentrations did not differ between sexes (men 115.0 ± 33.9 pg mL-1 vs. women 90.5 ± 40.8 pg mL-1; P = 0.2). The magnitude by which I/R injury attenuated endothelium-dependent vasodilation did not differ between men (pre-I/R 5.4 ± 2.4% vs. post-I/R 3.0 ± 2.7%) and women (pre-I/R 6.1 ± 2.8% vs. post-I/R 3.7 ± 2.7%; P = 0.9). Our data demonstrate that I/R injury similarly reduces endothelial function in women in the early follicular phase of the menstrual cycle and age-matched men with similar estradiol concentrations.