Forearm vasodilator responses to a β-adrenergic receptor agonist in premenopausal and postmenopausal women.

Ronee E Harvey,John H Eisenach,Emma C Hart,Jill N Barnes,Michael J Joyner,Timothy B Curry,Nisha Charkoudian

doi:10.14814/phy2.12032

Abstract

Beta‐adrenergic vasodilator responses may be blunted in humans who are at an increased risk for hypertension. Because menopause is associated with an increase in blood pressure, we tested the hypothesis that forearm blood flow responses to the β‐adrenergic receptor agonist isoproterenol are blunted in older, postmenopausal women compared to young, premenopausal women. We used venous occlusion plethysmography to measure forearm blood flow in young premenopausal (26 ± 1 years; n = 13) and postmenopausal (61 ± 2 years; n = 12) women. Forearm blood flow and mean arterial pressure were measured at baseline and during isoproterenol infusion at 1.0, 3.0, 6.0, and 12.0 ng/100 mL tissue/min. The two groups did not differ in body mass index or mean arterial pressure. Baseline forearm blood flow was similar between young and postmenopausal women (3.7 ± 0.5 vs. 2.9 ± 0.4 mL/100 mL tissue/min, respectively; P > 0.05). At the lowest dose of isoproterenol, forearm blood flow vasodilator responses were lower in postmenopausal women compared with young women (5.8 ± 0.4 vs. 7.4 ± 0.3 mL/100 mL tissue/min, respectively; P < 0.05). Thereafter, forearm blood flow remained similar between the groups for the remaining isoproterenol doses. In conclusion, β‐adrenergic receptor‐mediated forearm vasodilator responses are blunted in healthy, older postmenopausal women at lower but not higher doses of isoproterenol. This suggests that in aging women, β‐adrenergic receptor‐mediated vasodilator responses may be blunted at a moderate level of stimulation while maximum receptor responses are preserved.

Highlights

The risk of developing hypertension is greater in young and middle-aged men than in women of the same age range (Burt et al 1995). This risk increases with age in both sexes, women have a more dramatic rise in hypertension prevalence after the onset of menopause, and this may even surpass that of men (Cutler et al 2008)
It is possible that the onset of menopause and related changes in blood pressure regulation are associated with decreased b-adrenergic receptor responsiveness
The primary findings of this study are (1) with increasing doses of isoproterenol infusion, both young premenopausal women and older postmenopausal women have a significant increase in vasodilation measured by forearm blood flow; (2) at a low dose of isoproterenol, forearm blood flow responses are blunted in postmenopausal women in comparison to young women; and (3) at higher doses of isoproterenol, vasodilator responses are similar between the two groups of women

Summary

Introduction

The risk of developing hypertension is greater in young and middle-aged men than in women of the same age range (Burt et al 1995). In comparison to normotensive men, those with borderline hypertension have a lower absolute forearm blood flow response to local infusion of isoproterenol, a nonselective b-adrenergic receptor agonist. Kneale et al demonstrated that young premenopausal women had a lower percent change in forearm blood flow than young men during local infusion of norepinephrine (Kneale et al 2000). Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society

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