title: PHI stimulates ACTH release from pituitary tumor cell.
abstract: The identification of PHI (the 27-amino acid peptide (P) having an N-terminal histidine (H) and a C-terminal isoleucine amide (I] in median eminence suggested that PHI influences the secretory function of the anterior pituitary. The effects of PHI on ACTH release from clonal mouse pituitary corticotrophs were investigated. The secretory response to PHI was correlated with a prior increase in cyclic AMP accumulation. Both cyclic AMP synthesis and ACTH secretion were increased by PHI in a concentration-dependent manner. PHI was a less effective agonist of cyclic nucleotide synthesis and ACTH secretion than VIP. The secretory response to PHI was blocked by the calcium channel antagonist, nifedipine, and by dexamethasone. Somatostatin and oxotremorine blocked both PHI-stimulated cyclic AMP formation and ACTH secretion. The observation that VIP in high concentrations can elicit ACTH secretion from normal rat anterior pituitary suggested that a VIP-like substance may modulate ACTH secretion. However, the finding that PHI does not elicit ACTH release from primary cultures of dispersed anterior pituitary, coupled to its relatively lower potency compared to VIP, indicate that corticotrophs are not an important target for PHI.
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D005768:Gastrointestinal Hormones / Q000494:pharmacology*; D051379:Mice; D010095:Oxotremorine / Q000494:pharmacology; D010451:Peptide PHI; D010455:Peptides / Q000494:pharmacology*; D010911:Pituitary Neoplasms / Q000378:metabolism*; D013004:Somatostatin / Q000494:pharmacology
chemical_list: D005768:Gastrointestinal Hormones; D010451:Peptide PHI; D010455:Peptides; D013004:Somatostatin; D010095:Oxotremorine; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D000242:Cyclic AMP; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine