Testosterone, dehydroepiandrosterone and 4-androstene-3, 17-dione concentrations in maternal and fetal plasma in the last days of ovine gestation.

Abstract

Catheters were implanted in the femoral artery, uterine vein and umbilical blood vessels of 12 pregnant ewes to obtain sequential plasma samples for the determination of testosterone, dehydroepiandrosterone and 4-androstene-3,17-dione by radioimmunoassay during the last weeks of gestation. Delivery occurred at 147.8 ± 0.7 days of gestation (mean ± SEM). The concentration of dehydroepiandrosterone was 12–27 times greater than that of testosterone or 4-androstene-3,17-dione which were of the same order of magnitude. The mean dehydroepiandrosterone concentration in all the uterine vein samples, 4.32 ± 0.50, was significantly greater than in the femoral artery, 2.97 ± 0.19 ng/ml (mean ± SEM). An analysis of variance of these data grouped by 1-day intervals showed a progressive decrease in plasma dehydroepiandrosterone in the uterine vein as the time of parturition approached. A similar analysis for 4-androstene-3,17-dione in umbilical vein plasma samples showed a significant increase to 550 ± 108 pg/ml (mean ± SEM) in the last day of gestation. There was a tendency for the values of dehydroepiandrosterone and testosterone to be greater in the fetal than in the maternal samples, while the levels of 4-androstene-3,17-dione were greater in the femoral than in the umbilical artery. The results are compatible with the hypothesis that the rate of transformation of extraplacental dehydroepiandrosterone to other C1 9 steroids, and perhaps estrogens, increases during the last few days of pregnancy.