Opposite Effects of Prolactin and Corticosterone on the Expression and Activity of 3β-Hydroxysteroid Dehydrogenase/Δ5-Δ4 Isomerase in Rat Skin

Abstract

In rat skin, type IV is the major 3β-hydroxysteroid dehydrogenase/ δ5-δ4 isomerase (3β-HSD) isoenzyme expressed. Although types I and II 3β-HSD mRNAs are also present in the skin, their level 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 3β-HSD mRNA levels as well as 3β-HSD enzymatic activity in hypophysectomized adult rats of both sexes. Skin 3β-HSD activity was measured by the conversion of [14C]-dehydroepiandrosterone into [14C]-androstenedione, whereas ribonuclease protection assay using a specific type IV cRNA probe was used to assess mRNA levels. Intact male and female rats show a similar level of skin 3β-HSD activity, although hypophysectomy caused opposite effects, a decrease being observed in males while an increase was observed in hypophysectomized female animals. We next studied the effects of hyperprolactinemia, corticosterone, and l-thyroxine, in hypophysectomized animals. L-thyroxine was found to stimulate 3β-HSD expression and activity in male rats whereas no significant effect was observed on the already elevated levels in hypophysectomlzed female rats. Corticosterone caused an inhibition of type IV 3β-HSD mRNA levels and activity in both male and female animals. Hyperprolactinemia achieved by pituitary implants inserted under the kidney capsule stimulated the expression of type IV mRNA as well as 3β-HSD enzymatic activity in hypophysectomized male and female animals. The present data demonstrate the multihormonal regulation of 3β-HSD/isomerase expression and activity in the rat skin