Highly vectorial secretion of inhibin by primate Sertoli cells in vitro

Having recently demonstrated highly vectorial and FSH-stimulated inhibin secretion by immature rat Sertoli cells in vitro, we wished to determine if vectorial secretion of inhibin was also characteristic of primate Sertoli cells. By adapting techniques for isolation of Sertoli cells from testes of the immature rat and cynomolgus monkey. Sertoli cells were isolated from immature baboon testes. Sertoli cells were then plated onto matrix-impregnated porous filters and cultured in twin chamber assemblies in fully defined, supplemented HEPES-buffered Eagles medium. Inhibin was measured in conditioned culture media by an heterologous RIA validated for primate inhibins. Throughout 28 days of culture immunoreactive inhibin was readily detectable in the upper chambers whereas inhibin was undetectable or just detectable in the lower chambers. The median ratio of upper to lower chamber inhibin content was 15.3 under basal conditions rising to 41 under FSH stimulation. Inhibin secretion into the upper chamber was increased 2.5 +/- 0.4 times by stimulation with ovine FSH (100 ng/ml). We conclude that immature Sertoli cells from a nonhuman primate demonstrate FSH-responsive and highly vectorial secretion of inhibin almost exclusively into the upper chamber. These data suggest that during maturation mammalian Sertoli cells secrete inhibin vectorially mainly from the apical surface of the cell towards the seminiferous tubular lumen. The predominance of inhibin secretion into the seminiferous tubule during testicular maturation suggests that inhibin may have an important paracrine or autocrine role in the developmental biology of spermiogenesis.