Abstract
Abstract
Changes in rat uterine weight and uterine blood flow (UBF) between Days 4 and 12 of pseudopregnancy (PSP: Day 0 = ovulation) were monitored and correlated with the respective fluctuations in serum progesterone (P) and estradiol (E) levels. Rats were monitored for UBF using a square-wave electromagnetic blood flow monitor. Serum P and E levels were estimated by radioimmunoassay. Parallel changes in uterine weight and UBF were observed between Days 4 and 9 of PSP, each exhibiting a peak on Day 6 before declining to basal levels on Day 9. Serum E levels remained relatively constant throughout PSP, ranging between 5 and 7.5 pg/ml. In contrast, serum P levels exhibited peaks (Days 8-9) when UBF and uterine weights were lowest, and lower levels when the uterine parameters were elevated (Days 6-7). These data suggest that fluctuations in the ratio of E to P (rather than the respective, absolute levels of each) induce the changes observed in uterine weight and UBF during PSP in the rat.
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