GROWTH HORMONE-RELEASING HORMONE-RECEPTOR MESSENGER-RNA IS PRESENT INRAT TESTIS

A growth hormone-releasing hormone (GHRH) mRNA and peptide have been i dentified in rat and human testis and have been localized to spermatog enic cells in rat. Treatment of Sertoli cells with a GHRH analog incre ases intracellular cAMP and increases levels of c-fos and stem cell fa ctor (SCF) mRNAs, suggesting that a GHRH receptor exists in these cell s. in order to determine whether a GHRH receptor mRNA is present in ra t testis, we have used the reverse transcriptase-polymerase chain reac tion (RT-PCR) on RNA from whole testis and from germ, Sertoli and Leyd ig cells. After RT-PCR using two sets of primers, spanning the regions from nucleotides 1265 to 1548 and from nucleotides 866 to 1285 of the GHRH receptor mRNA, products of the expected sizes were seen in all c ell types evaluated. GHRH receptor mRNA was most abundant in Sertoli a nd germ cells, and less abundant in Leydig cells. Sequence analysis re vealed that the two products were identical to the pituitary GHRH rece ptor mRNA. Treatment of Sertoli cells with rat GHRH increased GHRH rec eptor mRNA levels in a dose-dependent manner. We conclude that a GHRH receptor is present in low abundance in rat testis, and that its produ ction in Sertoli cells is regulated by GHRH.