Ovarian hormones in man: their effects on resting vascular tone, angiotensin converting enzyme activity and angiotensin II‐induced vasoconstriction

Abstract

Aims Oestrogens in women have been shown to cause vasodilation which may re¯ect alterations in the activity of vascular angiotensin converting enzyme (ACE) and/or sensitivity to angiotensin II. The aim of this study was to assess the effect of ovarian hormones on vascular tone, vascular ACE activity and vasoconstriction to angiotensin II in males. Methods Eight volunteers were randomised in a crossover design to oestradiol, medroxy-progesterone, and placebo. Vasoconstriction to angiotensin I and angiotensin II was assessed by forearm plethysmography. Results Although baseline forearm¯ow was increased with oestradiol, suggesting generalized vasodilation, there were no changes in the vasoconstrictor responses to angiotensin I or angiotensin II. Medroxy-progesterone affected neither baseline¯ow nor vasoconstrictor responses. The results expressed as percentage reduction in¯ow (mean t s.d.) were: angiotensin I 48 pmol ml x1 : placebo x48t14%; oestradiol x42t16%; medroxyprogesterone x43t8% and for angiotensin II 16 pmol ml x1 : placebo x42t10%; oestradiol x39t11%; medroxyprogesterone x46t13%. Conclusions Acute administration of oestradiol caused vasodilation in males, the effect was not due to alterations in vascular ACE activity or to altered sensitivity to angiotensin II.

Reduced vasorelaxation to estradiol and G-1 in aged female and adult male rats is associated with GPR30 downregulation

“…In denuded rat aortic rings, there is no sex difference in E 2 -induced vasodilation (9), and E 2 -induced vasorelaxation is independent of sex in rat tail arteries (10). Effects of E 2 on vascular reactivity are also evident in human males, as clinical studies show an improvement in blood flow following infusion of conjugated equine estrogens or oral E 2 (2,17). Although males used in the current study were gonad intact, castration has no effect on the vasodilatory response to E 2 in rat aortic strips and tail arteries (6,10).…”

Effects of oestrogen‐only and oestrogen–progestogen replacement therapy upon circulating angiotensin I‐converting enzyme activity in postmenopausal women

“…Another factor to be determined is the minimum time necessary for changes in ACE activity to be apparent following commencement of HRT. An acute effect is unlikely because treatment of men within 24 h prior to study with either oral oestradiol valerate or medroxyprogesterone acetate was not seen to influence plasma ACE activity (Lee et al ., 2000).…”

Effect of Progesterone on Peripheral Blood Flow in Prepubertal Female Anesthetized Pigs

“…Others have shown that vaginal implants of progesterone in non-pregnant ovariectomized sheep increased nitric oxide synthase expression in the endothelium of the uterine artery but not in that of the omental, renal or mammary arteries [2], and that progesterone relaxes pre-contracted segments of small saphenous artery of the rat [3]. Also, it has been reported in humans that acute intra-arterial progesterone did not significantly affect forearm blood flow, particularly that mediated by endothelial mechanisms [4, 5], and that progesterone applied as a vaginal cream decreased forearm blood flow [6]. …”