Effects of transdermal estrogen administration on peripheral vascular responsiveness in menopausal women

This study was designed to evaluate the peripheral vascular responses to acute estrogen replacement. According to a cross-over, double-blind study design, we randomized nine healthy postmenopausal women (time lapse from menopause to >1 year; mean age±SD 45.4±11.7 years) to treatment with transdermal patches of estradiol-17beta or matched placebo. The estrogen patch was rated to assure a plasma concentration of substance of more than 100 pg/ml after 8–10 hours of treatment. Forearm blood flow (ml/100 ml/minute), local vascular resistance (mmHg/ml/100 ml/minute), venous volume (ml/100 ml), and venous compliance (ml/100 ml/mmHg) were measured in supine resting subjects by the straingauge venous occlusion plethysmography. Plasma concentration of norepinephrine (pg/ml) was quantified by HPLC-ED. Estradiol-17beta produced increase in forearm blood flow and decrease in local vascular resistance. The drug reduced circulating norepinephrine concentrations. There were no significant changes in mean arterial pressure or heart rate. Venous volume and venous compliance were both enhanced by estrogen administration. The peripheral circulatory changes are attributed to a direct activity of estradiol-17beta on arterial and venous wall and may in part reflect a modulation of estrogen on peripheral sympathetic tone.