Ovarian Hormones in Man: Their Effects on Resting Vascular Tone, Angiotensin Converting Enzyme Activity and Angiotensin II-induced Vasoconstriction

Aims: Oestrogens in women have been shown to cause vasodilation which may reflect 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 flow 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 flow nor vasoconstrictor responses. The results expressed as percentage reduction in flow (mean +/- s.d.) were: angiotensin I 48 pmol ml-1: placebo -48 +/- 14%; oestradiol -42 +/- 16%; medroxyprogesterone -43 +/- 8% and for angiotensin II 16 pmol ml-1: placebo -42 +/- 10%; oestradiol -39 +/- 11%; medroxyprogesterone -46 +/- 13%.

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.