OPPOSITE EFFECTS OF PROLACTIN AND CORTICOSTERONE ON THE EXPRESSION AND ACTIVITY OF 3-BETA-HYDROXYSTEROID DEHYDROGENASE DELTA(5)-DELTA(4) ISOMERASE IN RAT SKIN/

In rat skin, type IV is the major 3 beta-hydroxysteroid dehydrogenase/ Delta(5)-Delta(4) isomerase (3 beta-HSD) isoenzyme expressed. Although types I and II 3 beta-HSD mRNAs are also present in the skin, their l evel of expression is about two orders of magnitude lower than that of type IV. In this study, we have investigated the control of type IV 3 beta-HSD mRNA levels as well as SP-HSD enzymatic activity in hypophys ectomized adult rats of both sexes. Skin 3 beta-HSD activity was measu red by the conversion of [C-14]-dehydroepiandrosterone into [C-14]- an drostenedione, whereas ribonuclease protection assay using a specific type IV cRNA probe was used to assess mRNA levels. Intact male and fem ale rats show a similar level of skin 3 beta-HSD activity, although hy pophysectomy caused opposite effects, a decrease being observed in mal es while an increase was observed in hypophysectomized female animals. We next studied the effects of hyperprolactinemia, corticosterone and 1-thyroxine in hypophysectomized animals. L-thyroxine was found to st imulate 3 beta-HSD expression and activity in male rats whereas no sig nificant effect was observed on the already elevated levels in hypophy sectomized female rats. Corticosterone caused an inhibition of type IV 3 beta-HSD mRNA levels and activity in both male and female animals. Hyperprolactinemia achieved by pituitary implants inserted under the k idney capsule stimulated the expression of type IV mRNA as well as 3 b eta-HSD enzymatic activity in hypophysectomized male and female animal s. The present data demonstrate the multihormonal regulation of 3 beta -HSD/isomerase expression and activity in the rat skin.