Acetylcholine-mediated relaxation in rat thoracic aorta is enhanced following acute exposure to physiological concentrations of 17beta-estradiol.
We investigated the effects of short-term exposure to low concentrations of 17beta-estradiol on vasorelaxation using an in vitro rat thoracic aortic ring preparation. Supraphysiological levels of 17beta-estradiol directly relaxed phenylephrine-contracted rings. Although acute incubation (20 min) with 1-100 nM of the female sex hormone did not have any significant effect on phenylephrine-contracted rings, relaxation evoked by acetylcholine was significantly potentiated. In contrast, calcium ionophore A23187-elicited endothelium-dependent relaxation as well as cromakalim- and sodium nitroprusside-mediated endothelium-independent relaxation was unchanged following the same regime with 17beta-estradiol. These results demonstrate that short-term treatment with physiologically relevant levels of 17beta-estradiol, which on their own have no effect, enhances endothelium-dependent relaxation by acetylcholine. The vascular effects observed herein may partly account for some of the improved acute vasodilatory responses reported with 17beta-estradiol on blood flow in humans.
Teoh
H
H
Department of Pharmacology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
Leung
S W
SW
Quan
A
A
Huang
M
M
Man
G S
GS
Man
R Y
RY
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000502:physiology; D000001:Calcimycin / Q000494:pharmacology; D019806:Cromakalim / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology*; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D009126:Muscle Relaxation; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology*
D007476:Ionophores; D014665:Vasodilator Agents; D019806:Cromakalim; D009599:Nitroprusside; D000001:Calcimycin; D004958:Estradiol; D000109:Acetylcholine