Uterine blood flow and its distribution after chronic estrogen and progesterone administration.

The rates and distributions of uterine blood flow (UBF) were measured in conscious castrated ewes during estradiol, progesterone, and combined-hormone regimens. Supplemental progesterone decreased the magnitude of UBF observed on estradiol alone. Progesterone favored distribution of UBF to the uterine caruncles and estradiol favored distribution to the myometrium and uterine cervix. Proportionate endometrial blood flows were similar on all hormone regimens. These observations suggest that estradiol secretion may not be responsible for the definitive increase in UBF observed during ovine pregnancy.