Effects of growth hormone-releasing hormone-related peptide on stem cell factor expression in cultured rat Sertoli cells

The growth hormone-releasing hormone(GHRH) gene produces a precursor molecu le that contains GHRH and a carboxyl-terminal peptide that we have named GH RH-related peptide (GHRH-RP). This peptide, like GHRH, stimulates the expre ssion of stem cell factor (SCF), an important reproductive and hematopoieti c cytokine, in vitro and in vivo. In the present study, using primary cultu res of rat Sertoli cells, we compared the time course of action and the lev el of SCF stimulation seen following treatment with GHRH-RP and GHRH. Addit ionally, we investigated the activity of a truncated peptide, p75-92NH2, wh ose sequence is contained within GHRH-RP, All three of these peptides were shown to stimulate the steady-state levels of SCF mRNA to a comparable degr ee. However, the time course of action for GHRH-RP differed markedly from t hat of GHRH. GHRH-RP and p75-92NH2, similar to GHRH, induce SCF expression, at least in part, via the activation of the protein ki nase A/cyclic adeno sine monophosphate intracellular signaling pathway.