Uterine blood flow in relation to endogenous hormones during estrous cycle and early pregnancy

Abstract

To evaluate the extent to which endogenous hormones in peripheral blood can account for uterine blood flow (UBF), rates of blood flow and concentrations of estrone (E1), estradiol (E2), and progesterone (P4) were measured simultaneously in four sheep during the estrous cycle and the first 3 wk of pregnancy. During the estrous cycle, UBF was inversely related to the concentration of P4 (P less than 0.01) and directly related to (E1 + E2)/P4 (P less than 0.01). There was no animal in which UBF was related to estrogen alone. No statistically significant relationship between endogenous hormones and UBF was detected in any ewe during the first 3 wk of pregnancy. Data support the idea that UBF varies during the estrous cycle in relation to peripheral concentrations of P4 and (E1 + E2)/P4 but leaves open the nature of the relationship in early pregnancy.

Adaptations to reduction of endometrial surface available for placental development in sheep

“…Given in pharmacological doses, this hormone will induce overgrowth of caruncles (Alexander & Williams, 1966) and growth of uterine blood vessels (Phelps, 1946;Williams, 1948;Caton et al, 1974a) and does affect regulation of uterine blood flow (Caton et al, 1974a;Caton, Abrams, Lackore, James & Barron, 1974b;Caton et al, 1980;Roman-Ponce, Caton, Thatcher & Lehrer, 1983). Ewes differ with respect to the amount of progestagen released per kg of fetal, placental and uterine tissues during the last weeks of pregnancy and this amount is proportional to the subsequent weight of the lamb (Caton, Kalra & Wilcox, 1983).…”

Development and Use of an Ovarian Synchronization Model to Study the Effects of Endogenous Estrogen and Nitric Oxide on Uterine Blood Flow During Ovarian Cycles in Sheep1

“…Using intact ewes, Greiss and Anderson [12] reported that UBF is elevated during the periovulatory period in association with behavioral receptivity to a ram. Ford et al [13][14][15][16] and Roman-Ponce et al [17] reported that the higher the estrogen/progesterone (P 4 ) ratio in intact animals, the greater the magnitude of UBF. However, in studies using cycling cows, ewes, and sows, the timing and magnitude of the pattern of UBF of individual animals was quite variable [16,17] compared with very low, nearly nonexistent variability in the ovx model.…”

“…Ford et al [13][14][15][16] and Roman-Ponce et al [17] reported that the higher the estrogen/progesterone (P 4 ) ratio in intact animals, the greater the magnitude of UBF. However, in studies using cycling cows, ewes, and sows, the timing and magnitude of the pattern of UBF of individual animals was quite variable [16,17] compared with very low, nearly nonexistent variability in the ovx model. While this made the ovx model a vastly predictable and easier model to study than the intact sheep, it may not, however, represent what is actually occurring in the uterus during the estrous cycle.…”

Relationships Between Uterine Blood Flow, Peripheral Sex Steroids, Expression of Endometrial Estrogen Receptors and Nitric Oxide Synthases During the Estrous Cycle in Mares

“…Variations in uterine blood flow in cycling mares have been attributed to changes in circulating estrogen concentrations. However, due to a weak correlation between the resistance to uterine blood flow and plasma estrogen concentrations, other factors may also regulate uterine blood flow [2].Changes in uterine blood flow during the estrous cycle in many species are mediated mainly by estrogens [5]; although flow was enhanced by high plasma estradiol concentrations [6,7] and decreased during the luteal phase [8,9], the mechanisms involved have not been elucidated. Estrogens appear to act via two pathways: the genomic and non-genomic pathways [10].…”

“…Changes in uterine blood flow during the estrous cycle in many species are mediated mainly by estrogens [5]; although flow was enhanced by high plasma estradiol concentrations [6,7] and decreased during the luteal phase [8,9], the mechanisms involved have not been elucidated. Estrogens appear to act via two pathways: the genomic and non-genomic pathways [10].…”