Histochemical localization of 3 - and 17 -hydroxysteroid dehydrogenases in the male reprodutive tract of the domestic fowl (Gallus domesticus)

Synopsis 3- and 17-hydroxysteroid dehydrogenase activities were studied histochemically in the male reproductive tract of the domestic fowl. 3-hydroxysteroid dehydrogenase was NAD⁺-linked and was capable of metabolizing the three substrates used, namely, pregnenolone, 17-hydroxypregnenolone and dehydroepiandrosterone. 17-hydroxysteroid dehydrogenase oxidized testosterone in the presence of NAD⁺ or NADP⁺. The pattern of distribution of formazan granules was essentially the same with all the substrates used, and they were located in the Leydig cells, seminiferous tubules and the lining epithelia of the entire excurrent duct system of the testis except the rete testis. The activity of both enzymes appeared to be highest in the ductuli efferentes and decreased distally along the tract. The evidence suggests that steroid synthesis may occur in the epithelial lining of the excurrent ducts as well as in the cells of the testis.