RAT LEYDIG-CELLS BIND PLATELET-DERIVED GROWTH-FACTOR THROUGH SPECIFICRECEPTORS 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 pr ecursors, we tested the hypothesis that these cells might be a target for PDGF. We also investigated a possible production of a PDGF-like su bstance by Leydig cells in culture and the distribution of PDGF-like m aterial in the rat testis using immunohistochemistry. PDGF was found t o bind specifically to high affinity receptors on the surface of purif ied adult rat Leydig cells. Conditioned medium from cultured Leydig ce lls 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 s tudies revealed specific staining for PDGF in the Leydig cells of adul t rat testis. Taken together these observations suggest that PDGF may play a role in the local control mechanisms of testicular function.