Sertoli cells in culture release a pregnancy specific beta1 glycoprotein-like substance

The possibility that pregnancy-specific beta1 glycoprotein (PSG) is released by Sertoli cells was investigated by using reverse hemolytic plaque assays which enable the visualization of release from individual cells in culture. We found that the proportions of cells releasing PSG increased gradually in 3-day old cultures prepared from animals of increasing age (10-, 20-, and 40-day old animals). The gradual appearance of PSG-releasing cells during this period differed markedly from that of transferrin (TF)-releasing cells, suggesting that the age-related development of PSG-releasing cells is regulated in a specific manner. PSG cells were also found in Sertoli cell cultures prepared from stage-associated seminiferous tubule segments of adult rat testes. The percentages of PSG plaque-forming cells differed from one stage-associated culture to another with maximal proportions associated with stages III-V and XIII, and minimal proportions found in stages VII, and IX-XI. The abundance of Sertoli cells that released PSG from stage to stage differed markedly from those that released TF indicating that modulatory processes specific for PSG are also present in the adult testis. Finally, PSG cells were also identified immunocytochemically in cultures prepared from staged tubule segments. The proportion of PSG staining cells from stage to stage were found to be virtually indistinguishable from those identified with plaque assays. When taken together, these results show clearly that Sertoli cells in culture release a PSG-like molecule. Moreover, this release appears to be controlled in an age-related and stage-dependent manner, suggesting that Sertoli cells may be central to PSG function in the testis.