Metabolic Cooperation between Sertoli Cells and Peritubular Cells in Culture*

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Abstract
Studies were undertaken to examine the mechanisms involved in the cooperation between peritubular cells and Sertoli cells. Sertoli cells were isolated from 16-day-old Wistar rats using trypsin and collagenase treatments. In the first phase of experiments, the Sertoli cells and peritubular cells were grown in parabiotic culture tubes in which a 0.22-μm Millipore filter barrier was placed between the two cell types. This allowed the medium to pass into both chambers while restricting contact between the two cell types. No increase in the secretion of androgen-binding protein was observed under these conditions compared to that in parabiotic chambers that contained only Sertoli cells. In the second phase of experiments, peritubular cells or a continuous cell line (LM cells) were prelabeled with [3H]uridine or [3H]thymidine. Unlabeled Sertoli cells were then added to the cultures of peritubular cells and grown in the presence of 1 mM unlabeled precursor for 2 days. The cells were then fixed, cleared of unincorporated precursor with trichloroacetic acid, and prepared for light autoradiography. The cells were also studied by autoradiography after RNAse treatment. Parallel cultures were studied by transmission electron microscopy. These studies demonstrated that peritubular cells can transfer RNA or a RNA precursor molecule to Sertoli cells. This phenomenon occurs only when the cells are in direct contact. Only a small amount of labeling was observed over Sertoli cells cocultured with LM cells that had been prelabeled with [3H]uridine. No transfer of DNA was observed with either cell type. RNAse treatment did not abolish the label when tested before fixation. However, the label was greatly reduced when RNAse was tested after the cell membranes were damaged with ethanol-acetic acid, indicating that the labeled molecule was intracellular. Transmission electron micrographs demonstrated numerous dense-coated vesicles associated with the cytoplasmic membranes of adjacent Sertoli cells and peritubular cells. These studies indicate that the secreted products of peritubular cells are not responsible for the increased secretion of androgenbinding protein observed in Sertoli cells cocultured with peritubular cells. Furthermore, peritubular cells can metabolically cooperate with Sertoli cells in vitro by transferring RNA or RNA precursors when these two cells are juxtaposed. It is not known, however, whether these two phenomena are related.

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