title: Oral estrogen replacement therapy increases forearm reactive hyperemia accompanied by increases in serum levels of nitric oxide in postmenopausal women.
abstract: The present study sought to determine the correlation between the vasodilator response of forearm resistance vessels and the circulating levels of nitric oxide (NO) after the administration of oral estrogen for 12 weeks to postmenopausal women. We classified postmenopausal women into two groups: those treated with conjugated equine estrogen (0.625 mg daily) orally for 12 weeks (n = 24) or those who received no treatment (control group, n = 8). Forearm blood flow was measured using strain-gauge plethysmography during hyperemia to evaluate endothelium-dependent vasodilation, and after sublingual nitroglycerin administration to evaluate endothelium-independent vasodilation. Serum levels of nitrite/nitrate (metabolites of NO) and lipid parameters were measured. Basal forearm blood flow, body weight and heart rate were similar in each group. After 12 weeks of estrogen administration, the maximal forearm blood flow response during reactive hyperemia and the serum level of nitrite/nitrate each showed a significant increase from 26.9 +/- 1.9 to 37.9 +/- 3.5 ml/min per 100 ml tissue (p < 0.01), and from 25.2 +/- 2.2 to 37.5 +/- 3.7 mumol/l (p < 0.05), respectively. No increases were seen in controls. The changes in forearm blood flow after sublingual nitroglycerin were similar before and after 12 weeks of estrogen administration. The increase in maximal forearm blood flow with reactive hyperemia was significantly correlated with the increase in nitrite/nitrate in the group administered estrogen (r = 0.48, p < 0.05). There was no significant correlation between maximal forearm blood flow with reactive hyperemia, nor any change in serum lipids, blood pressure or other parameters. In conclusion, the 12-week administration of oral estrogen increased forearm reactive hyperemia in postmenopausal women, probably via an increase in the production of NO.
authors.affiliation: Department of Obstetrics and Gynecology, School of Medicine, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Sanada
authors.forename: Y
authors.initials: Y
authors.lastname: Higashi
authors.forename: K
authors.initials: K
authors.lastname: Nakagawa
authors.forename: S
authors.initials: S
authors.lastname: Sasaki
authors.forename: I
authors.initials: I
authors.lastname: Kodama
authors.forename: T
authors.initials: T
authors.lastname: Sakashita
authors.forename: M
authors.initials: M
authors.lastname: Tsuda
authors.forename: K
authors.initials: K
authors.lastname: Ohama
mesh_terms: D001835:Body Weight; D004730:Endothelium, Vascular / Q000502:physiology; D015914:Estrogen Replacement Therapy; D005260:Female; D005542:Forearm / Q000098:blood supply*; D006339:Heart Rate; D006801:Humans; D008875:Middle Aged; D009566:Nitrates / Q000097:blood; D009569:Nitric Oxide / Q000097:blood*; D009573:Nitrites / Q000097:blood; D017698:Postmenopause; D014655:Vascular Resistance; D014664:Vasodilation
chemical_list: D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide