STUDIES ON OESTRIOL SYNTHESIS FROM DEHYDROEPIANDROSTERONE SULPHATE IN HUMAN PREGNANCY

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Abstract
The pathway of oestriol (OE3) synthesis from dehydroepiandrosterone sulphate (DHAS) was examined in human pregnancy at midterm, from both foetal and maternal compartments. In the first series of experi?ments, H3-labelled DHAS and Cl4-labelled oestrone sulphate (OE]S) were administered into the intact foeto-placental circulation. Oestrone (OEi), 17[beta]-oestradiol (OE2) and OE3 formed during the 20 minutes after injection were isolated from the placenta, foetus and urine of the mother. The following observations were mad: a) conversion to OE3 was greater from DHAS than OElS, b) more OE3 was formed from DHAS than OEi and OE2, c) the H3/Cl4-ratios of the urinary OE3 were higher than those of OEI and OE2. In the second series of experiments, three pregnant subjects were given the same com?bination of sulphurylated precursors via the antecubital vein, and OEi, OE2 and OE3 were isolated from their urine. In contrast to the foeto-placental studies: a) OElS was converted to urinary OE3 in greater yield than was DHAS, b) more OEi and OE2 were formed from DHAS than was OE3, c) the H3/C1*- ratios of the three urinary oestrogens were similar to each other. In addition, the specific activity of OE3 was lower than that of OEi and OE2 with respect to both H3 and Cl4. These results suggest that DHAS circulating within the foeto-placental compartment is converted to OE3 via both phenolic and neutral intermediates, whereas DHAS originating from the maternal circulation is converted to OE3 largely via a phenolic pathway. Approximately 80% of the OE3 formed within the foeto-placental compartment was transferred to the mother within 20 minutes. This rapid transport may explain the usefulness of urinary OE3 determinations in the assessment of foetal viability.