title: Estrogen-induced augmentation of endothelium-dependent nitric oxide-mediated vasodilation in isolated rat cerebral small arteries.
abstract: We examined chronic effects of 17beta-estradiol (E(2)beta) on the responses of isolated rat anterior cerebral small arteries to vasoactive substances with special reference to endothelial function. Female Sprague-Dawley rats were separated into four groups: (1) sham-operated group (Sham), (2) sham-operated plus E(2)beta treated group (Sham+E), (3) ovariectomized group (OVX), (4) ovariectomized plus E(2)beta treated group (OVX+E). 5-Hydroxytryptamine (5-HT) (10(-10)-10(-3) M) and U46619 (10(-15)-10(-8) M) induced concentration-dependent contractions in the cerebral small arteries. The 5-HT- and U46619-induced contractions were not affected by pretreatment with 3 x 10(-5) M N(omega)-nitro-L-arginine methyl ester (L-NAME). No significant difference in high potassium (80 mM)- and the agonists-mediated contractions was observed among the four groups. Administration of acetylcholine (ACh) (10(-9)-10(-3) M) and sodium nitroprusside (SNP) (10(-8)-10(-3) M) caused dose-related relaxations in the cerebral small arteries precontracted by 10(-8) M U46619. Chronic treatment with E(2)beta caused a significant potentiation of the ACh-induced relaxations in the Sham+E and OVX+E groups. The dose-response curve for ACh in the OVX group was quite similar to that obtained with the Sham group. The ACh-induced relaxation was reduced significantly by pretreatment with 3 x 10(-5) M L-NAME, and an additional treatment with 10(-3) M L-arginine reversed significantly the L-NAME-induced inhibition. The removal of endothelial cells produced a significant reduction of the ACh-induced relaxation. Indomethacin (10(-5) M) did not alter the ACh-induced relaxation. The findings suggest that E(2)beta potentiates ACh-induced endothelium-dependent relaxation in rat anterior cerebral arteries and that the potentiation may be, in part, mediated by increasing production and release of endogenous NO from the endothelial cells.
authors.affiliation: The 1st Department of Physiology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto, 390-8621 Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Momoi
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Ikomi
authors.forename: Toshio
authors.initials: T
authors.lastname: Ohhashi
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002536:Cerebral Arteries / Q000187:drug effects / Q000502:physiology*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000502:physiology*; D005260:Female; D066298:In Vitro Techniques; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D010052:Ovariectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D004967:Estrogens; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009569:Nitric Oxide; D012701:Serotonin; D004958:Estradiol; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester