A novel peptide from the growth hormone releasing hormone gene stimulates Sertoli cell activity

The growth hormone releasing hormone (GHRH) gene is believed to produce a single functional peptide, GHRH (1). Although GHRH mRNA and peptide have been identified in various tissues, the only accepted function of GHRH is the stimulation of pituitary growth hormone. We have discovered that the GHRH mRNA encodes a second peptide that is abundant in testicular germ cells and specifically activates Sertoli cell expression of stem cell factor (SCF), a factor crucial for the normal progression of spermatogenesis (2). These observations suggest that the GHRH gene produces two distinct peptides, each with tissue-specific activities.