DEVELOPMENTAL EXPRESSION OF PLACENTAL TROPHOBLAST P-450 CHOLESTEROL SIDE-CHAIN CLEAVAGE, ADRENODOXIN AND DELTA(5)-3-BETA-HYDROXYSTEROID DEHYDROGENASE ISOMERASE MESSENGER RIBONUCLEIC-ACIDS DURING BABOON PREGNANCY/

The present study determined whether the elevation in oestrogen, which occurs with advancing baboon pregnancy, is associated with a developm ental increase in expression of the placental enzymes catalysing proge sterone synthesis. The mRNA levels for P-450 cholesterol side-chain cl eavage (P-450(scc)), adrenodoxin, and Delta(5)-3 beta-hydroxysteroid d ehydrogenase/isomerase (3 beta-HSD) were assessed by Northern blot ana lysis in placental syncytiotrophoblasts isolated from baboons in early (days 58-65), mid- (days 97-113) and late (days 161-175), gestation ( term=184 days). Placental villous tissue was dispersed and subjected t o 50 per cent Percoll density gradient centrifugation to obtain primar ily syncytiotrophoblasts. Mean (+/- S.E.) P-450(scc) mRNA level, expre ssed as a ratio of beta-actin in the syncytiotrophoblast-rich fraction , progressively increased with advancing pregnancy to a level in late gestation (1.81 +/- 0.28 arbitrary units) that was approximately sixfo ld (P<0.01) greater than in early gestation (0.31 +/- 0.08) and approx imately twofold greater (P<0.05) than in mid-gestation (0.97 +/- 0.24) . In contrast adrenodoxin mRNA expression was similar at early (0.97), mid- (1.14 +/- 0.12) and late (1.16 +/- 0.13) gestation. Syncytiotrop hoblast 3 beta-HSD mRNA levels also remained constant in early (1.69), mid- (1.89 +/- 0.41) and late (1.34 +/- 0.41) gestation. On the basis of these findings, we propose that villous syncytiotrophoblasts under go functional/biochemical differentiation, resulting in a coordinated upregulation of specific components of the steroid biosynthetic pathwa y required for progesterone biosynthesis during the course of primate pregnancy. (C) 1996 W. B. Saunders Company Ltd