STUDIES ON THE METABOLISM OF C-21 STEROIDS IN THE HUMAN FOETO-PLACENTAL UNIT

Abstract

ABSTRACT In situ perfusion of human midterm placentas with labelled pregnenolone and 17α-hydroxypregnenolone was carried out. Following perfusion with pregnenolone in two experiments, 80 and 90 per cent of the radioactive material recovered from the placenta and 25 and 29 per cent of that recovered from the perfusate was progesterone. These figures accounted for 17 and 13 per cent of the perfused dose. Perfusion with 17α-hydroxypregnenolone in three experiments indicated that 87, 66 and 73 per cent of the radioactive material recovered from the placentas and 48, 44 and 52 per cent of that found in the perfusates was 17α-hydroxyprogesterone. These figures represent 26, 17 and 17 per cent of the perfused material. Several polar metabolites of both pregnenolone and 17α-hydroxypregnenolone were also detected, but in amounts insufficient for their identification. It is suggested that conversion of circulating 3β-hydroxy-Δ5-precursors into α,β-unsaturated 3-ketones may be a major pathway in the placental synthesis of progesterone and 17α-hydroxyprogesterone.