IDENTIFICATION OF RECEPTOR TYROSINE KINASES IN THE RAT TESTIS

Evidence of receptor/ligand interactions that regulate testis cell fun ction was sought in order to broaden the current understanding of the molecular basis of testis cell function. Using reverse transcription a nd the polymerase chain reaction, we have obtained novel evidence for the expression of three mRNAs encoding receptor tyrosine kinases in th e adult rat testis: the platelet-derived growth factor type A receptor (PDGF-RA), the basic fibroblast growth factor receptor (flg), and fet al liver kinase 1 (Flk-1). A 6.8 kb transcript encoding the PDGF-RA wa s observed in RNA prepared from testes of rats aged day 5 through adul t, with a decline in relative abundance with increasing age after day 17. Analysis of mRNA from isolated cell preparations (day 21 Sertoli c ells, adult Leydig cells, round spermatids, and primary spermatocytes) and testes depleted of specific cell types [ethane dimethane sulfonat e (EDS)-treated and cryptorchid] indicated that the Leydig cell was th e predominant source of this mRNA in the adult testis. The addition of PDGF-BB to cultures of highly purified adult rat Leydig cell preparat ions resulted in a 40% increase in LH-stimulated testosterone producti on, confirming a role for this growth factor in regulation of Leydig c ell function. These data indicate that the Leydig cell is a principal site of action of PDGF in the testis. (C) 1993 Wiley-Liss, Inc.