Growth hormone-releasing factor stimulates adenylate cyclase activity in the anterior pituitary gland

Synthetic human pancreatic growth hormone-releasing factor (hpGRF)(1-40)-NH2 stimulates adenylate cyclase activity in rat anterior pituitary particulate fraction at an ED50 value of approximately 150 nM. GTP more than doubles the stimulatory effect of hpGRF and PGE2 on [32P] cyclic AMP formation. The present data show that hpGRF as well as PGE2, another potent stimulus of GH secretion, act at least partly, through GTP-dependent mechanisms in their coupling with adenylate cyclase.