Studies on the metabolism of C-21 steroids in the human foeto-placental unit. 2. Metabolism of pregnenolone sulphate by midterm placentas perfused in situ.

Abstract

ABSTRACT Two midterm human placentas were perfused in situ with pregnenolone-7α-3H sulphate and the unconjugated metabolites present in the placentas and perfusates were analyzed. Eighty-five and 54% of the radioactive material recovered from the placentas was in an unconjugated form, whereas only 1 and 3% of that found in the perfusates was unconjugated. Eighty-one and 76% of the unconjugated material recovered from the placentas was isolated as progesterone and 2 and 6% as pregnenolone. Fifty-two and 42% of the unconjugated material recovered from the perfusates was isolated as progesterone and 30 and 36% as pregnenolone. Of the total radioactive material administered 1.1 and 2.7% was isolated as progesterone and 0.24 and 0.45% as unconjugated pregnenolone. More than 90% of the conjugated radioactive material recovered from the perfusate was unchanged pregnenolone sulphate. The results indicate that the midterm placenta converts circulating pregnenolone sulphate into pregnenolone and progesterone and secretes both of these compounds to the foetus.