STUDIES ON THE AROMATISATION OF NEUTRAL STEROIDS IN PREGNANT WOMEN.

Abstract

ABSTRACT 16α-Hydroxy-dehydroepiandrosterone-7α-3H (16αHO-DHA), 16α-hydroxy-androstenedione-4-14C (16αHO-A) and 16α-hydroxy-testosterone-4-14C (16αHO-T) were synthesized. Human placentas were perfused in situ at midpregnancy with these steroids and the radioactive material recovered from the placentas and perfusates was analysed. In order to compare the aromatisation of 16α-hydroxylated and 16-desoxy precursors, in a second series of perfusions 16αHO-DHA was combined with differently labelled dehydroepiandrosterone (DHA) and 16αHO-T with testosterone (T). Following the perfusion of 16αHO-DHA, both 16αHO-A and oestriol (OE3) were isolated from the placentas and perfusates. No labelled androst-5-ene-3β,16α,17β-triol (Δ5-TRIOL) or 16αHO-T was detected in these sources. When 16αHO-A or 16αHO-T was perfused, OE3 was isolated from the placenta and perfusates. However, there was no interconversion between 16αHO-A and 16αHO-T. No oestrogenic ring D ketols were found in the placentas and perfusates in any of the experiments. The extent of aromatisation (judged from the amount of oestrogen isolated from the placenta and perfusate) was approximately the same following the perfusion of 16αHO-DHA, 16αHO-A, DHA and T, but was much lower when 16αHO-T was perfused. The low degree of aromatisation of 16αHO-T was associated with the presence of large amounts of unchanged 16αHO-T in the placentas as well as in the perfusates. The transfer of 16αHO-T to the maternal compartment was also much lower than that of the other precursors studied. It is concluded that the placental transfer and aromatisation of 16αHO-T is much lower than those of other oestrogen precursors. This condition might lead to the accumulation of this compound in the placenta. The placental metabolism of Δ5-TRIOL and 16αHO-DHA follow separate pathways with no interconversion until the stage of aromatisation, or possibly 19-hydroxylation.