Acute administration of 17 beta-oestradiol does not improve endothelium-dependent vasodilatation in young men

Studies have recently demonstrated that long-term oestrogen therapy improve s endothelium-dependent and endothelium-independent vasodilatation in the c onductance vessels of biological males. We sought to determine if an acute single dose of oestrogen might similarly improve vasodilator function in yo ung males. in a randomized, double-blind, placebo-controlled, crossover stu dy, we compared the effects of 1 mg of sublingual 17 beta-oestradiol (E-2) and placebo on endothelium-dependent and endothelium-independent vasodilata tion in the brachial artery using a non-invasive ultrasound technique. We r ecruited 30 young males based on a power calculation. Neither acute subling ual oestrogen nor placebo affected flow-mediated vasodilatation [5.32 +/- 0 .78% and 5.28 +/- 0.60% respectively (mean +/- S.E.M.), P = 0.94]. Response s to nitroglycerine were similar after oestrogen or placebo (16.01 +/- 0.86 % and 15.29 +/- 1.19%, P = 0.47). Basal blood flow and flow during reactive hyperaemia did not differ after oestrogen or placebo. Heart rate and blood pressure were similar during both treatment phases of the study. The absol ute change in serum oestradiol levels was greater after the oestrogen treat ment phase than after placebo (1509 +/- 87 versus -13 +/- 4 pmol/l, P < 0.0 001). Despite achieving supraphysiological oestradiol levels, the acute adm inistration of sublingual E-2 does not appear to improve endothelium-depend ent or endothelium-independent vasodilatation, at least acutely, in the bra chial artery of young males. In keeping with our previous study, these data suggest that a period of oestrogen 'priming' (possibly to induce receptor- mediated nitric oxide synthesis) may be required to yield an improvement in vascular function in males.