Steroidogenesis in the human fetal adrenal: a role for cholesterol synthesized de novo

Primary monolayer cultures of human fetal adrenal cells maintained in either lipoprotein-depleted or lipoprotein-supplemented media responded chronically to ACTH treatment with similarly increased steroid secretion. The principal steroid secreted into each medium was dehydroepiandrosterone sulfate. The presence of human low density lipoprotein (hLDL) in the medium enhanced the secretion of nonsulfoconjugated steroids, especially dehydroepiandrosterone. The secretion rate of 11 beta-hydroxyandrostenedione was similar to that of cortisol. In the absence of hLDL, ACTH increased cholesterologenesis to maintain the high rates of steroid secretion. After ACTH treatment, increased accumulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase, a rate-determining enzyme of cholesterol biosynthesis, was found. Immunoblot analysis demonstrated that this enzyme was a 97K protein in human fetal adrenal cells. Interestingly, the content of this enzyme in cells treated with ACTH in lipoprotein-depleted medium was similar to that in adrenal fetal zone tissue. This finding suggests that cholesterologenesis de novo in addition to plasma LDL is important as a source of steroid precursor in vivo in the human fetal adrenal gland.