Binding of 3H-Sertoli cell factor to rat anterior pituitary in vitro

The binding characteristics of Sertoli Cell Factor (SCF) to the anterior pituitaries were examined using tissue homogenates and cultured cells. Tritium-labeled SCF (3H-SCF), synthesized by rat Sertoli cells in vitro in the presence of 3H-leucine and partly purified by Sephadex gel chromatography, was used to the ligand. The binding of 3H-SCF to the pituitary homogenates or cultured cells was considerably greater (3-6X) compared to homogenates of brain, kidney, liver, spleen and testis. The pituitary binding at 37 C occurred after approximately 60 time dependent, and directly related to the receptor concentration. Maximum binding at 37 C occurred after approximately 60 min of incubation. Over 90% of the bound 3H-SCF was competitively inhibited by an excess of unlabeled SCF, but not by other substances. There was a good correlation between the binding of 3H-SCF and its biological activity, as evidenced by a selective suppression of basal FSH release in pituitary cell cultures. These data indicate that, in analogy to other protein hormones, specific binding to target cell receptors may represent an initial step of SCF action in the pituitary. The binding should also prove valuable in the development of a rapid radio-receptor assay for SCF and possibly for other inhibin preparations.