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

Abstract

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.

PIP: The size and distribution of uterine blood flow (UBF) under hormonal regimens was investigated in castrated ewes. Ewes were administered either 1) estradiol-17beta benzoate 2 mcg-kg-day for 21 days, 2) Regimen 1 plus 1 mg/kg/day progesterone caproate for 21 days, 3) an initial 2 mcg of estradiol followed by 1 mg/kg/day progesterone for 21 days, or 4) Regimen 1 for 14 days plus the progesterone regimen on Days 8-14. UBF showed a marked increase under all hormone regimens, then decreased to stable levels in the 3rd week. UBF on progesterone alone was significantly below UBF under Regimens 1 and 2 (p less than .05). Carnuncular flow under progesterone was twice that under estradiol. Proportionate flow to the myometrium and cervix was greater under the estradiol regimen. Endometrial blood flows did not differ under any of the regimens. The results do not support the premise that the increase in UBF during pregnancy is due to increased estrogen secretion.