Enhancement of 3[beta]-hydroxysteroid dehydrogenase-isomerase in the human fetal adrenal by removal of the soluble cell fraction

Abstract

To asses whether there is some factor in the soluble cell fraction which might result in inhibition of the 3[beta]-hydroxysteroid dehydrogenase-isomerase enzyme system in the human fetal adrenal, separate homogenate and microsomal fractions of fetal adrenal tissue were incubated wtih isotopic pregnenolone and dehydroepiandrosterone. The amount of the [Delta]4-3-ketosteroid, androstenedione, found in the microsomal preparation was 22-27 times higher than that in the homogenate. No labeled C12-[Delta]4-3-ketosteroids were found.The data are interpreted as suggesting that inhibition of the formation of [Delta]4-3-ketosteroids occured in the homogenate, even though this enzyme capacity is present. The exact nature of this inhibition was not demostrated. The data further imply a deficiency of a pregnenolone-specific 3[beta]-hydroxysteroid dehydrogenase-isomerase system and suggest substrate specificity for this enzyme function.