In seven nonpregnant sheep studied either acutely or chronically there was an increase in total uterine blood flow after the systemic, 2-min infusion of 1.0 μg/kg of estradiol-17, β. The mean control flow was 20 ± 3 ml/min and the mean flow, measured approximately 2 hr after estradiol, was 283 ± 50 ml/min (P < 0.001). The chronic preparations showed a mean increase in flow that was 186 ml/min greater than that measured in the acute preparations. The blood flow to all uterine tissues increased markedly after the injection of estrogen, and the distribution of flows within the uterus was not altered. The correlation coefficient between total arterial flow to the uterus, measured by the microsphere method, and the sum of blood flows in the left and right uterine arteries, measured with electromagnetic flow probes, was 0.987. The blood flow to the mammary gland and vagina also increased after the administration of estradiol. This study demonstrates that the vasculature of all of the tissues of the nonpregnant ovine uterus, endometrium, myometrium, and caruncles is extremely sensitive to the vasodilatory effects of estradiol-17, β. Inasmuch as the arterioles supplying blood to the caruncles are the same as those that perfuse the placental cotyledons in the pregnant state, these data support the hypothesis that estrogens play an important role in the regulation of placental blood flow.
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health