Vascular reactivity in men and women of reproductive age

This study was undertaken to document vascular reactivity in both phases of normal menstrual cycles and anovulatory cycles of women receiving oral contraceptives and to compare vascular reactivity of women in the follicular phase of the normal menstrual cycle with that of men of a similar age group.

Forearm blood flow was measured with plethysmography in 15 women with ovulatory cycles during the follicular and luteal phases of the normal cycle, at equivalent times in 14 women receiving oral contraceptives, and in 15 age-matched men. Changes in forearm blood flow, an index of vascular reactivity, were measured during a randomly ordered brachial artery infusion schedule of norepinephrine, sodium nitroprusside, angiotensin II, and Nomega-monomethyl-L -arginine and were analyzed with repeated measures analysis of variance.

Forearm blood flow responses were similar in the two phases of the normal cycle. Responses were similar between women with ovulatory cycles and users of oral contraceptives, apart from a significantly greater response to angiotensin II in the oral contraceptive group during the medication phase than during the withdrawal phase (P =.027). Basal forearm blood flow was higher in men than in women (7 +/- 1.6 vs 5 +/- 1.4 mL/100 mL per minute; P =.015), and men demonstrated a significantly greater vasoconstrictor response to norepinephrine (P <.05) than did women.

Vascular reactivity is similar in the two phases of the normal menstrual cycle, but women who use oral contraceptives have an exaggerated response to angiotensin II during the medication phase. Men demonstrate greater vascular reactivity to norepinephrine than do women, perhaps because of the lack of estrogen-mediated protective effects and increased adrenergic activity.