Effects of Synthetic Ovine Corticotropin-Releasing Factor, Glucocorticoids, Catecholamines, Neurohypophysial Peptides, and Other Substances on Cultured Corticotropic Cells*

Synthetic ovine corticotropin-releasing factor (CRF) is a 41-residue peptide with high potency and intrinsic activity to stimulate the secretion of ACTH and j8-endorphinlike immunoactivity (β-End-LI) by cultured adenohypophysial corticotropic cells. The action of CRF in vitro can be potentiated by the weaker secretagogues, vasopressin, oxytocin, epinephrine, norepinephrine, and angiotensin II. CRF-mediated secretion of ACTH and β-End-LI is noncompetitively inhibited by pretreatment of cells with glucocorticoids. Long term exposure of adenohypophysial cells to CRF results in an increase in total medium plus cell ACTH in the cultures, suggesting that CRF can enhance rates of ACTH synthesis as well as release. CRF also stimulates the secretion of β-End-LI by corticotropic cells cultured from the neurointermediate lobe. Higher concentrations of CRF are required to stimulate secretion by this cell type than by anterior lobe corticotropic cells. These in vitro results are consistent with CRF playing a major phy...