Estrogen and tamoxifen modulate cerebrovascular tone in ovariectomized female rats

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

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Author(s)

  • Suk-Ying Tsang
  • Xiaoqiang Yao
  • Franky L. Chan
  • Chi-Ming Wong
  • Zhen-Yu Chen
  • Ismail Laher

Detail(s)

Original languageEnglish
Pages (from-to)78-82
Journal / PublicationHypertension
Volume44
Issue number1
Publication statusPublished - Jul 2004
Externally publishedYes

Abstract

Postmenopausal estrogen deficiency increases the incidence of cerebrovascular disease. However, hormone replacement therapy is associated with an increased cardiovascular risk. Tamoxifen is a selective estrogen receptor modulator with estrogenic effects on cardiovascular risk factors, but its long-term impacts on cerebral vasculature are unknown. We hypothesized that chronic 17β-estradiol or tamoxifen treatment exerted similar effects in reducing cerebrovascular tension in ovariectomized rats. We therefore determine whether (1) chronic 17β-estradiol treatment could influence vasomotor activities, (2) chronic tamoxifen therapy could exert an estrogen-like or estrogen-antagonistic effect, and (3) acute exposure to estrogen could mimic the effect of 17β-estradiol. Isometric tension was measured in cerebral arteries from female rat groups: control, ovariectomy, ovariectomy plus 17β-estradiol treatment, ovariectomy plus tamoxifen treatment, and ovariectomized rats treated with tamoxifen and 17β-estradiol. Ovariectomy enhanced cerebrovascular contractions to endothelin-1 or CaCl2, but not to U46619 or phenylephrine. 17β-Estradiol therapy reversed these effects. Chronic tamoxifen treatment exerted estrogen-like actions by reversing ovariectomy-induced enhancement of vessel tone without antagonizing the effect of chronic 17β-estradiol treatment. Ovariectomy enhanced the relaxing potency of nicardipine, and 17β-estradiol treatment prevented this effect. Acute exposure to 10-9 mol/L 17β-estradiol or 10-8 mol/L tamoxifen did not modulate contractions in rings from nonoperated female rats. In conclusion, ovariectomy differentially enhances agonist-induced cerebrovascular tone, an effect that was reversed by estrogen therapy. Tamoxifen does not act as an estrogen antagonist; instead, it functions as an estrogen agonist during estrogen deficiency. Thus, tamoxifen may confer beneficial effects similar to estrogen in cerebrovascular vessels.

Research Area(s)

  • Cerebral arteries, Estrogen, Rats, Vasoconstriction

Bibliographic Note

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Citation Format(s)

Estrogen and tamoxifen modulate cerebrovascular tone in ovariectomized female rats. / Tsang, Suk-Ying; Yao, Xiaoqiang; Chan, Franky L. et al.
In: Hypertension, Vol. 44, No. 1, 07.2004, p. 78-82.

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review