In vitro progesterone and testosterone production by the rat placenta during pregnancy

In vitro placental production of progesterone, testosterone, 20 alpha-hydroxy-4-pregen-3-one, and 17 beta-estradiol (E2) was investigated throughout pregnancy in the rat by RIA. Incubations of minced placental preparations with the steroidogenic enzyme inhibitors aminogluthethimide phosphate [2-(p-aminophenyl)2-ethyl-glutarimide phosphate] and cyanoketone (2 alpha-cyano-4,4,17 beta-trimethyl-17 beta-hydroxy-5-androsten-3-one resulted in a dose-related inhibition of progesterone and testosterone production. Progesterone production (picograms per mg tissue) from 2-h incubations of minced placental preparations was low on day 10 of pregnancy (day 1 = morning sperm are found in vaginal washings), peaked on day 12 (mean +/- SE, 281 +/- 32), decreased on day 14 (183 +/- 20), and returned to low levels (less than 80 pg/mg tissue X 2 h) from day 16 to term. Testosterone production (picograms per mg tissue/2 h) was not detectable on day 10, progressively increased to a peak of 46 +/- 7 on day 18, and decreased to term. Production of 20 alpha-hydroxy-4-pregnen-3-one or E2 was negligible in these minced placental preparations. Addition of androstenedione to placental incubates did not result in E2 production. Total steroid production per placenta was calculated as a function of the average placental weight for a given day. Total placental progesterone production was low on day 10 and rose to high levels (greater than 12 ng/placenta X 2 h) from day 12 to term. Total testosterone production progressively increased to a peak of 19 +/- 3 ng/placenta X 12 h on day 18 and decreased to term. These results demonstrate that throughout pregnancy, the rat placenta is an active steroidogenic tissue.