Estrogen improves abnormal norepinephrine-induced vasoconstriction in postmenopausal women

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Abstract
An exaggerated blood pressure response to mental stress in postmenopausal women has been reported but the underlying mechanism is not clear. In the present study, we examined the role of estrogen in the blood pressure response to mental stress. Hemodynamic responses to mental stress and constrictor responses to norepinephrine were compared in 18 premenopausal (mean ± SD age 33 ± 5 years), 22 postmenopausal women (62 ± 7 years) and 13 postmenopausal women with estrogen replacement therapy (58 ± 8 years). Premarin was infused in 10 postmenopausal women to determine whether estrogen attenuates norepinephrine-induced vasoconstriction. The hemodynamic responses to a standard mental arithmetic test were measured. Norepinephrine (12.5, 25, 50, 100 ng/min) was infused at 0.5 ml/min for 5 min via the dorsal hand vein. Norepinephrine (100 ng/min) combined with premarin (200 μg/min) was infused into the dorsal hand vein of postmenopausal women. Changes in venous diameter were measured by ultrasonography using a 7.5 MHz transducer. All study subjects were healthy, normotensive and had normal lipid profiles. The postmenopausal women showed a significantly greater blood pressure response to the mental arithmetic test than the premenopausal women or those taking estrogen replacement therapy (P < 0.01). Norepinephrine induced significant dose-dependent vasoconstriction in all three groups (P < 0.001). The postmenopausal women showed significantly greater constriction in response to norepinephrine than the premenopausal women and those taking estrogen replacement therapy (P < 0.02). Premarin significantly attenuated the norepinephrine-induced vasoconstriction in the postmenopausal women (P < 0.001). Healthy, normotensive postmenopausal women showed an exaggerated blood pressure response to mental stress. An increased vasoconstriction in response to norepinephrine and loss of estrogenmediated vasodilation may contribute to the increased blood pressure response to stress in postmenopausal women without estrogen replacement therapy.