Testicular secretion of inhibin in the Gottingen miniature pigs

To determine the cellular source of inhibin, immunolocalization of inhibin alpha, beta A and beta subunits were investigated in our study. Strong positive staining of inhibin alpha, subunit was observed in Sertoli cells and weak positive staining in Leydig, cells. Inhibin beta A subunit was stained positively in Sertoli cells, whereas inhibin beta subunit was positively stained in Leydig cells. From the results of enzyme linked immunosorbent assay (ELISA), Pro-alpha C was abundant in both the circulation and the testis. The testis contained much higher concentrations of inhibin B than inhibin A. In peripheral serum, inhibin B was detectable, whereas inhibin A was undetectable. In addition, we investigated the immunolocalization of two steroidogenic enzymes, 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and cytochrome P450 (aromatase). We found that 3 beta-HSD and aromaatase was confined to the Leydig cells. These results strongly suggest that the dimeric (bioactive) inhibin is mainly secreted by Sertoli cells. Inhibin B may offer a clinically useful peripheral marker of testicular function.