Vasodilating effect of estrogen on the human umbilical artery.

The effects of estradiol, estrone and estriol on the tonus of the isolated vascular segments of human umbilical artery were studied by a perfusion technique. Estradiol (10 microgram/ml), estrone (10 microgram/ml) or estriol (2 and 10 microgram/ml) produce relaxation of the vascular bed which was reflected in a significant reduction in basal pressure of segments perfused at constant rate. A dose-dependent relationship was demonstrated for estriol. The time dependence and extent of relation were similar for all three natural estrogens.