title: Estrogen replacement suppresses stress-induced cardiovascular responses in ovariectomized rats.
abstract: We assessed the hypothesis that chronic estrogen replacement in ovariectomized rats has the beneficial effect of suppressing stress-induced cardiovascular responses through endothelial nitric oxide synthase (eNOS). We employed a radiotelemetry system to measure blood pressure and heart rate (HR). Female Wistar rats aged 11 wk were ovariectomized and implanted with radiotelemetry devices. After 4 wk, the rats were assigned either to a placebo-treated group (Placebo; n=6) or a group treated with 17beta-estradiol (Estrogen; n=8) subcutaneously implanted with either placebo- or 17beta-estradiol (1.5 mg/60-day release) pellets under anesthesia. These rats underwent either of the two types of stress after 4 wk of estrogen or placebo treatment. Cage-switch stress and restraint stress rapidly and continuously elevated the mean arterial pressure (MAP) and HR both in the Placebo and Estrogen groups. However, the MAP and HR responses to cage-switch stress and the MAP but not HR response to restraint stress were attenuated significantly in the Estrogen group compared with the Placebo group. A NOS inhibitor, NG-nitro-L-arginine methyl ester, given in drinking water, reduced the difference in the pressor response to cage-switch between the Estrogen and Placebo groups. In addition, Western blot analysis showed that eNOS expression in the mesentery was increased in the Estrogen group compared with the Placebo group. Thus for the first time we showed that mesenteric eNOS overexpression could explain at least partly why chronic estrogen treatment suppressed the enhanced cardiovascular responses to psychological stress in the ovariectomized rat.
authors.affiliation: Dept. of Environmental Health, Faculty of Life Science and Human Technology, Nara Women's University, Kita-Uoya Nishi-machi, Nara 630-8506, Japan. kmorimot@cc.nara-wu.ac.jp
authors.forename: Keiko
authors.initials: K
authors.lastname: Morimoto
authors.forename: Youko
authors.initials: Y
authors.lastname: Kurahashi
authors.forename: Kaori
authors.initials: K
authors.lastname: Shintani-Ishida
authors.forename: Natsuko
authors.initials: N
authors.lastname: Kawamura
authors.forename: Mariko
authors.initials: M
authors.lastname: Miyashita
authors.forename: Masami
authors.initials: M
authors.lastname: Uji
authors.forename: Nobusuke
authors.initials: N
authors.lastname: Tan
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Yoshida
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects* / Q000503:physiopathology*; D004334:Drug Administration Schedule; D004958:Estradiol / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D008643:Mesentery / Q000201:enzymology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D010052:Ovariectomy; D051381:Rats; D017208:Rats, Wistar; D013312:Stress, Physiological / Q000503:physiopathology*
chemical_list: D004958:Estradiol; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat