CRF stimulates adenylate cyclase activity in the intermediate lobe of the pituitary gland

Ovine corticotropin-releasing factor (CRF) stimulates adenylate cyclase activity in homogenate of the intermediate lobe of the bovine pituitary gland at an ED50 value of 150 nM. GTP increases the stimulatory effect induced by CRF as well as by the beta-adrenergic agonist isoproterenol on [32P]cyclic AMP formation in rat pars intermedia homogenate. In addition, GTP is required for inhibition by dopamine of the stimulatory action of both CRF and isoproterenol. The present data show that CRF stimulates adenylate cyclase activity in the intermediate lobe of the pituitary gland at least partly through a GTP-dependent mechanism. Moreover, dopamine can interfere with the action of CRF as well as that of isoproterenol, thus indicating that the neurohormone could be involved, in addition to beta-adrenergic agents, as stimulator of pars intermedia cell activity.