Vascular actions of 17 beta-oestradiol in rat aorta and mesenteric artery

1 It has been proposed that the cardiovascular protective actions of 17 bet a-oestradiol may involve calcium antagonistic actions. We have examined the effects of 17 beta-oestradiol on contractions to noradrenaline and KCl in male rat small mesenteric artery and aorta. 2 In rat mesenteric artery, 17 beta-oestradiol (10 mu m) significantly redu ced the maximum contraction to noradrenaline (67.7 +/- 5.8% of control) and KCl (38.8 +/- 3.1% of control) without affecting potency. 3 In rat aorta, 17 beta-oestradiol (10 mu m) also significantly reduced con tractions to noradrenaline (77.5 +/- 4.8% of control), and the effects were mimicked by droloxifene (10 mu m). The effect of oestrogen was not prevent ed by the protein synthesis inhibitor cycloheximide (10 mu m). In experimen ts carried out in calcium-free solution in which calcium stores were deplet ed, 17 beta-oestradiol (10 mu m) significantly reduced the contraction to c alcium restoration in rat aorta. 4 In aorta from female rats, 17 beta-oestradiol (10 mu m) significantly red uced contractions to noradrenaline (73.6 +/- 10.8% of control), but this ef fect of oestrogen was not prevented by cycloheximide (10 mu m). 5 In summary, 17 beta-oestradiol diminishes the maximum contractile respons e to noradrenaline in both rat small mesenteric artery and aorta, an effect which at least in the aorta is mimicked by the oestrogen receptor antagoni st/partial agonist droloxifene, and may be due to restriction of calcium en try by a nongenomic action.