Patterns of steroid biosynthesis by human adrenals incubated in vitro with [7alpha-3H) pregnenolone: changes with (a) gestational age, (b) incubation period and (c) weight of incubated tissue

SUMMARY Human adrenal tissue was sliced and incubated with 25 μc [7α-3H]-pregnenolone. The percentage conversion of radioactive precursor to dehydroepiandrosterone (DHA), DHA sulphate, androstenedione, 11β-hydroxyandrostenedione, cortisol and 11-deoxycortisol was estimated by the reverse isotope dilution technique. Incubations of both adult and foetal adrenal slices gave reproducible results. The duration of the incubation period was an important factor affecting the pattern of radioactive steroids synthesized, the adult adrenal pattern being dissimilar to that of the foetal adrenal. A direct proportional relationship between the weight of the incubated tissue and the biosynthesis of cortisol from exogenous [7α-3H]-pregnenolone was not established. The production of DHA sulphate relative to free DHA increased markedly from 12 to 27 weeks gestation. When incubated for 2 hr. the combined production of DHA and DHA sulphate relative to cortisol and androstenedione decreased with gestational age. There was evidence for considerable 3β-hydroxysteroid dehydrogenase activity in foetal adrenals at 12 to 27 weeks gestation.