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  • Title: Regulation of 3 beta-hydroxysteroid dehydrogenase in adrenocortical cells: effects of angiotensin-II and transforming growth factor beta.
    Author: Rainey WE, Naville D, Mason JI.
    Journal: Endocr Res; 1991; 17(1-2):281-96. PubMed ID: 1652433.
    Abstract:
    The maintenance of optimal steroidogenesis in adrenocortical cells primarily depends on the chronic action of ACTH to promote the synthesis of the various steroid metabolizing enzymes. In the steroidogenic pathway, the ratio of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) to 17 alpha-hydroxylase cytochrome P450 (P-450(17 alpha)) plays a key role in determining the final steroid products released by adrenal cells. The differences in these enzymes are particularly important when one considers the adrenal zones and the secretion of the zone-specific steroids. In the present study we have investigated the regulation of 3 beta HSD with regard to its enzyme activity, levels of protein and changes in specific mRNA encoding for this enzyme. Following eight days in primary culture, bovine adrenocortical (BAC) cells were found to respond to both ACTH and Bu2 cAMP by increased cortisol production. In addition, 3 beta HSD activity, enzyme protein and mRNA levels were increased in response to both factors. The increases varied from 2-fold for activity to 5-7 fold for mRNA. ACTH and Bu2cAMP also greatly increased P-450(17 alpha) from the near undetectable levels in control cells. In order to examine the possibility of differential regulation of these adrenal steroidogenic enzymes we determined the effects of angiotensin II (A-II) and transforming growth factor beta (TGF beta) on the levels of these enzymes. Both of these factors decreased the ACTH-stimulated levels of P-450(17 alpha) enzyme and mRNA to near nondetectable levels observed within control cells. In addition, these compounds inhibited the ACTH induction of 3 beta HSD. While the mechanism of TGF beta action is not clear, A-II probably is acting through protein kinase C. Indeed the protein kinase C activating phorbol ester, TPA, mimicked the inhibitory effects of A-II on 3 beta HSD and P450(17 alpha). It is important to point out, however, that the effects of A-II and TGF beta on P450(17 alpha) activity appeared more pronounced than their action of 3 beta HSD. This observation may relate to the relative stability of 3 beta HSD as compared to P450(17 alpha). Taken together these data indicate that, while A-II and TGF beta each decrease the levels of steroid-metabolizing enzymes, a differential regulation is observed in that P-450(17 alpha) protein and activity levels are much more sensitive to treatment with these factors.
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