Sex differences in peripheral vascular adrenergic receptors.

Although the incidence of many vascular diseases differs in men and women, sex differences in vascular physiology have not been extensively examined in human in vivo studies. The present study compared finger blood flow responses of normal men and women with brachial artery infusions of adrenergic agonists and with other neurally and nonneurally mediated procedures. In response to phenylephrine and clonidine, men showed significant dose-related vasoconstriction while women did not. In response to isoproterenol, men showed significant dose-related vasodilation while women did not. There were no sex differences in response to intra-arterial nitroglycerin or digoxin or to reactive hyperemia, procedures that do not act through adrenergic receptors. These data show that the sensitivity and/or density of peripheral vascular adrenergic receptors is lower in women than in men. There were no sex differences in response to reflex vasoconstriction or to intra-arterial tyramine, suggesting that neurally released norepinephrine acts at alpha-adrenergic receptors that are spatially removed from those that respond to circulating catecholamines.