RAT LEYDIG-CELLS BIND PLATELET-DERIVED GROWTH-FACTOR THROUGH SPECIFIC RECEPTORS AND PRODUCE PLATELET-DERIVED GROWTH FACTOR-LIKE MOLECULES

The platelet-derived growth factor (PDGF) is a major mitogen for cells of mesenchymal origin. Because Leydig cells arise from mesenchymal precursors, we tested the hypothesis that these cells might be a target for PDGF. We also investigated a possible production of a PDGF-like substance by Leydig cells in culture and the distribution of PDGF-like material in the rat testis using immunohistochemistry. PDGF was found to bind specifically to high affinity receptors on the surface of purified adult rat Leydig cells. Conditioned medium from cultured Leydig cells competed with I-125-labeled PDGF for binding to the Leydig cells. The secretion of PDGF receptor-competing activity was stimulated in a dose-dependent manner by the tropic hormone hCG. Immunohistochemical studies revealed specific staining for PDGF in the Leydig cells of adult rat testis. Taken together these observations suggest that PDGF may play a role in the local control mechanisms of testicular function.