Studies of the mechanisms of action of corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) in the ovine anterior pituitary: evidence that CRF and AVP stimulate protein phosphorylation and dephosphorylation.
This study was undertaken to determine the roles of corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) in the regulation of adrenocorticotropin (ACTH) secretion in perfused ovine anterior pituitary (AP) cells and their ability to cause protein phosphorylation and dephosphorylation in these cells. Freshly dispersed ovine AP cells were maintained in a miniperifusion chamber and ACTH secretion was monitored every 20 s. When cells were perfused with CRF (1 nM, 5 min) or AVP (1 nM, 5 min), ACTH release was increased 20-fold and 12-fold, respectively. When an ovine AP cell membrane fraction was incubated with either CRF or AVP, CRF stimulated the phosphorylation of at least 11 proteins and the dephosphorylation of at least 5 phosphoproteins, whereas AVP caused the phosphorylation of at least 15 proteins and the dephosphorylation of 5 proteins. A comparison of the proteins phosphorylated by CRF or AVP with those phosphorylated by cAMP or protein kinase C activators suggested that the hormone-stimulated phosphorylation may also involve unidentified protein kinases. Additionally, at least eight proteins appeared to be phosphorylated by both CRF and AVP. Furthermore, in the case of four particular proteins both CRF and AVP stimulated phosphorylation at low concentrations of Ca2+ (0.1-1 microM), but at high concentrations of Ca2+ (10-100 microM) CRF or AVP triggered dephosphorylation of these proteins.(ABSTRACT TRUNCATED AT 250 WORDS)
Liu
J P
JP
Endocrinology Unit, John Hunter Hospital, Newcastle, NSW, Australia.
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002118:Calcium / Q000008:administration & dosage / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism; D010477:Perfusion; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D012756:Sheep
D008565:Membrane Proteins; D010750:Phosphoproteins; D001127:Arginine Vasopressin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D004533:Egtazic Acid; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D011494:Protein Kinases; D011493:Protein Kinase C; D002118:Calcium