Δ5-3β-Hydroxysteroid Dehydrogenase Δ4-5-Isomerase Activity and Metabolism of Dehydroepiandrosterone in Rat Preputial Gland

After intracardial injection of [1,2-3H] dehydroepiandrosterone ([3H]DHA) into female rats, [3H]DHA was found to accumulate and was metabolized in the preputial gland, but not in the diaphragm. The identified metabolites of [3H]DHA in the preputial gland were δ4-androstenedione-3α,17β-diol. Cells were isolated from the preputial gland after treatment with trypsin and collagenase III, and centrifugation in Ficoll gradients. Activity of the enzyme complex δ5-3β-hydroxysteroid dehydrogenase δ4–5-isomerase (3β-HSD) responsible for transforming DHA into δ4-androstenedione was found mainly in the 105,000 g pellet (microsomal fraction) of homogenates of the isolated cells. It used preferentially NAD over NADP as a coenzyme, with a pH optimum at 8.5. The apparent Km for DHA was 5.5 × 10-5 M, and the Vmax was 1.72 nmol/min/mg microsomal protein. These findings indicate that DHA is preferentially taken up by the preputial gland where it undergoes metabolism to form more potent androgens, and suggest that DHA may have important androgenic influence on the preputial gland