STUDIES ON THE AROMATISATION OF NEUTRAL STEROIDS IN PREGNANT WOMEN

Abstract

ABSTRACT Tracer amounts of dehydroepiandrosterone-4-14C (DHA-4-14C) and dehydroepiandrosterone-7α-3H sulphate (DHAS-7α3H) were injected simultaneously into a uterine artery in two patients twelve to fifteen minutes prior to therapeutic interruption of pregnancy at laparotomy and the amniotic fluid, foetuses, placentas and urine samples were analysed for radioactive material. No radioactivity was found in the amniotic fluid. Regardless of the tracer administered, approximately 80 per cent of the radioactive material recovered from the placentas was in an unconjugated (free) form, whereas more than 80 per cent of the radioactivity present in the foetuses was in a conjugated form. More than 67 per cent of the total radioactive material in the two placentas and more than 87 per cent of that in the two foetuses was present as phenolic material. Approximately half of this phenolic material was identified as oestrone (OE1) and 17β-oestradiol (OE2). The 3H to 14C ratio of OE1 and OE2 isolated from the foetuses and urine specimens was lower than the ratio of the injected material. Corresponding 3H to 14C ratios in placental OE1 and OE2 were higher than those in foetal or urinary OE1 and OE2. Labelled oestriol (OE3) could be detected in the placentas, but not in the foetuses. However, a 16-hydroxylated phenolic intermediate (probably 16α-hydroxyoestrone) was found in one foetus studied. The results indicate that the DHA and DHAS of the maternal circulation can serve as direct precursors to placental OE2 and OE1 and as indirect precursors – via a foetal intermediate – to placental OE3. Both compounds reach the foetus mostly as phenolic material, the free form being a better precursor than the sulphate. It is suggested that – around midpregnancy at least – the human placenta functions as a barrier limiting the transfer to the foetus of androgens present in the maternal circulation.