QUANTITATIVE ASSESSMENT OF THE PRINCIPAL STEROIDS FORMED BY HUMAN PLACENTAS PERFUSED WITH LABELLED CHOLESTEROL IN VITRO

ABSTRACT Three midgestation and three term placentas were perfused in vitro each with 5 mCi of [7α-3H] cholesterol. Perfusions were carried out at 37°C for 120 minutes, using diluted blood oxygenated with an air + CO2 mixture (23.1% O2 + 3.6% CO2). Radiochemically homogenous pregnenolone, progesterone, dehydroepiandrosterone and 17β-oestradiol were isolated from each placenta and each perfusate. Carbon-14 labelled internal standards were used in order to assess procedural losses. On an average 0.01 per cent of the perfused cholesterol was converted to the four steroids studied by midgestation placentas and 0.015 per cent by term placentas. Approximately equal amounts of the individual steroids were recovered from the placentas and from the perfusates. The amounts of pregnenolone + progesterone isolated exceeded those of dehydroepiandrosterone + 17β-oestradiol by a factor of 7 to 8. It is suggested that the human placenta is capable of converting circulating cholesterol not only to pregnenolone and progesterone, but also to dehydroepiandrosterone and 17β-oestradiol.