Estrogen replacement increases beta-adrenoceptor-mediated relaxation of rat mesenteric arteries.
The purpose of the present study was to determine whether estrogen replacement in ovariectomized rats could modulate arterial diameter responses to beta-adrenoceptor activation. Under relaxed conditions (0.1 mM papaverine) there were no differences in the lumen diameter of isolated, pressurized (50 mm Hg) mesenteric arteries from nontreated (191.7 +/- 13.8 microns; n = 19) versus those from estrogen-treated (190.1 +/- 11 microns; n = 14) ovariectomized Sprague-Dawley rats. In arteries precontracted with noradrenaline (0.3-1 microM), isoprenaline (0.01-10 microM)-induced relaxation was significantly increased in arteries from ovariectomized estrogen-treated rats (52.4 +/- 2% of the maximal relaxation induced by 0.1 mM papaverine, vs. 33.3 +/- 6.5%; p < 0.01). The half-maximal concentration value was 0.04 +/- 0.05 microM in estrogen-treated rats and 0.4 +/- 0.1 microM in nontreated rats (p < 0.01). This response was inhibited by propranolol (1 microM) in both groups to a comparable extent (61.5%), and was unaffected by endothelial removal. Forskolin (0.01-10 microM) induced similar concentration-dependent vasodilation in arteries of both groups of rats with no differences in sensitivity or maximal response. These results suggest that isoprenaline acts through beta-adrenoceptors present on vascular smooth muscle and that estrogen replacement enhances the relaxant responses induced by beta-adrenoceptor activation by an endothelium-independent mechanism.
Ferrer
M
M
Department of Obstetrics and Gynecology, University of Vermont College of Medicine, Burlington, USA.
Meyer
M
M
Osol
G
G
D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D015914:Estrogen Replacement Therapy; D005260:Female; D007545:Isoproterenol / Q000494:pharmacology; D008638:Mesenteric Arteries / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D010208:Papaverine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology
D011943:Receptors, Adrenergic, beta; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D004958:Estradiol; D010208:Papaverine; D007545:Isoproterenol; D009638:Norepinephrine