Purpose: It is thought that oestrogen replacement therapy may reduce the conversion of angiotensin I to angiotensin II in postmenopausal women by inhibiting angiotensin converting enzyme. We sought to determine the effects of 3 months oestrogen replacement therapy (ERT) on the response to angiotensin I and II in postmenopausal women.
Methods: Eighteen postmenopausal women were randomised to either three months of 2mg oral oestradiol or placebo in a double blind, placebo controlled, protocol. Change in forearm blood flow (FBF), in response to brachial arterial infusion of increasing concentrations of angiotensin I and angiotensin II was measured, pre-randomisation, after 1 months randomised therapy and after 3months therapy, using venous occlusion plethysmography.
Results: Oestrogen treatment had no effect on baseline FBF. The mean (SD) peak reductions in FBF with 64 pmol/min angiotensin I pre-randomisation, after 1 month and after 3 months treatment with placebo were 62(11), 65(15) and 57(8)%. The corresponding reductions with the peak dose of angiotensin II (16 pmol/min) were 53(8), 48(12) and 47(11)%. In the oestradiol group, the peak responses to angiotensin I were 56(8), 53(11) and 44(29)% pre-randomisation, after 1 months treatment and after 3 months treatment. The corresponding reductions in response to angiotensin II were 37(15), 47(15) and 45(19)%. Oestradiol did not affect the response to either angiotensin I or angiotensin II.
Conclusion: This study does not support the idea that ERT might exert a cardioprotective effect through inhibition of the renin-angiotensin system.
