In the present investigation the role of serum lipoproteins in fetal adrenal steroidogenesis was evaluated. Human fetal adrenal tissue was maintained in organ culture for 6 days in the presence or absence of ACTH. The culture medium contained either human serum (10%, vol/vol) or lipoprotein-poor serum (10%, vol/vol) with or without low density lipoprotein (LDL), high density lipoprotein, or very low density lipoprotein. The medium was changed daily and assayed for pregnenolone sulfate, dehydroepiandrosterone sulfate (DS), and cortisol. In the absence of ACTH, steroid secretion decreased to negligible rates, regardless of the presence or absence of lipoprotein in the culture medium. However, the cumulative secretions of DS, pregnenolone sulfate, and cortisol for the entire 6-day culture period in the presence of ACTH plus optimal amounts of LDL or human serum were 72.5 and 72.2 μg/mg tissue protein, respectively. These values were greater than those observed in the absence of lipoproteins (37.6 μg/mg tissue protein) or when very low density or high density lipoprotein was included in the medium (35.2 and 54.0 μg/mg protein, respectively). When various concentrations of LDL were employed, maximal secretion rates for DS and cortisol were observed when the concentration of LDL protein was 150-200 μg/ml. It is concluded that plasma lipoprotein cholesterol is used by human fetal adrenal tissue in culture for steroidogenesis, and that LDL appears to be the lipoprotein preferred as a source of cholesterol for steroidogenesis by this tissue.
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