| Abstract: | Sertoli cells are a primary target for the action of follicle-stimulating hormone (FSH) in the testis. The purpose of this investigation was to verify ultrastructurally that FSH binds to receptors on the plasma membrane of isolated rat Sertoli cells. A relatively pure aliquot of Sertoli cells was obtained by first dissociating testicular tissue from immature rats with collagenase and then centrifuging the suspension in Percoll density gradients. Pre-embedding staining with the peroxidase anti-peroxidase (PAP) complex technique using anti-FSH beta as the primary antiserum localized endogenous receptor-bound FSH on the plasma membrane of isolated Sertoli cells. Staining was considered to be specific since membranes of Sertoli cells derived from hypophysectomized rats were not stained when subjected to the same procedure. Cytoplasmic vesicles in Sertoli cells from experimental, control, and hypophysectomized groups also stained with PAP. Staining of these structures appeared to be specific since it was obliterated by preabsorption of anti-FSH beta with FSH. Preabsorption with luteinizing hormone (LH) did not affect the staining of cytoplasmic vesicles. The results of this investigation provide the first evidence for ultrastructural localization of specific binding sites for anti-FSH beta on the cell membrane of isolated Sertoli cells using an unlabeled antibody technique, and they further support the contention that Sertoli cells are a primary target for the action of FSH. |
