Sertoli Cells in Culture Are Heterogeneous with Respect to Transferrin Release: Analysis by Reverse Hemolytic Plaque Assay*

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Abstract
It has been reported that not all Sertoli cells store the same product or respond morphologically to secretagogue stimulation. The following studies were performed to determine whether functional differences among these cells are also present with respect to the secretion of a product. Sertoli cells obtained from 18- to 20-day-old rats were cultured for 3 days and then subjected to reverse hemolytic plaque assays for transferrin (TF). Release of TF could be detected from only 62.7 .+-. 0.47% (mean .+-. SE; n = 4 experiments) of all cells in culture. Results obtained from immunocytochemical staining of different batches of cells from the same dispersions agreed quite closely with these plaque assay values, indicating that not all Sertoli cells in culture contain or secrete TF. Differences in the basal rate of TF release were observed among these secretors, as evidenced by a gradual appearance of plaques over an 8-h period. Addition of FSH, cAMP, or isoproterenol to the assay incubation mixture resulted in an acceleration in the rate of plaque formation. Although approximately twice as many secretors could be identified after 0.5 and 1 h of incubation in the presence of these agents than in their absence, it still required at least 4 h for the remainder of the TF cells to form plaques. This would indicate that only a portion of all TF secretors respond acutely to these modulators. Thus, our observations that not all Sertoli cells secrete TF, and those that do release this substance respond differently to at least three stimulatory agents demonstrate clearly that Sertoli cells are heterogeneous with respect to TF release. Moreover, these findings raise the possibility that differences in the functional capacity of individual cells may be an important factor contributing to the modulation of Sertoli cell secretion.