Estrogen Excretion of the Pregnant Baboon (Papio papio)

A radioimmunoassay for determination of urinary estrone (E1)1 excretion from pregnant baboons has been devised. Conjugates were hydrolyzed enzymically and E1 was extracted with diethyl ether. Following isolation by Sephadex LH-20 chromatography, E1 was assayed by competition with 3H-E1 for an estradiol-17β-BSA conjugate antiserum. During the 5 days after iv administration of 2.5 and 5.0 mg estradiol-17β to pregnant animals the increments in urinary E1 represented 52 and 57% of the dose, respectively, and thus supported our estimate of E1 excretion. E1 values in urine of nonpregnant animals were <15 µg/24 hr. Mean E, (μg/24 hr) excretion by 6 pregnant animals determined at 5-day intervals rose from 320 at 70 days to 640 at 175 days gestation. Daily determinations thereafter showed a further rise to 840 at term (184 days). Between 70 and 175 days the rate of increase of urinary E1 excretion was 3.0 ± 0.5 (SE) µ,g/24 hr and significantly different (p = < 0.01) from that during the final 9 days of gestation (29.8 ± 11.6 (SE) µg/24 hr). This 10-fold rate increase suggests a connection between estrogen production and parturition in this species. After delivery, E1 excretion fell rapidly and by 3 days postpartum was close to nonpregnant levels. A similar fall occurred at the time of spontaneous abortion, an indication that estrogen production depends on a functioning fetus and/or placenta. (Endocrinology95: 1759, 1974)