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Possible involvement of adenylyl cyclase-cAMP-protein kinase a pathway in somatostatin inhibition of growth hormone release from chicken pituitary cells.

Abstract
Somatostatin (SRIF) reduces growth hormone releasing hormone (GRF)-stimulated growth hormone (GH) release from avian and mammalian adenohypophyseal cells. The present studies examined the intracellular mechanisms mediating SRIF inhibition of GRF-stimulated GH release from chicken pituitary cells. Increases (P less than 0.05) in GH release were observed in the presence of (1) GRF; (2) the adenylyl cyclase stimulator, forskolin; (3) a cAMP analog, 8-bromo-cAMP; (4) the phosphodiesterase inhibitor 3-isobutyl-l-methyl-xanthine (IBMX) combined with GRF; (5) a tumor-promoting phorbol ester and protein kinase C activator, phorbol 12-myristate, 13-acetate (PMA); (6) a diacylglycerol analog, 1,2-dioctanoyl-glycerol (DiC8); and (7) a calcium ionophore, A23187, alone and in combination with PMA. Somatostatin (10 ng/ml) reduced the release of GH stimulated by GRF, forskolin, and 8-bromo cAMP and the GRF-provoked release of GH in the presence of IBMX (P less than 0.05). Somatostatin, however, did not influence GH release in the presence of the protein kinase C activators, PMA or DiC8, or the calcium ionophore A23187. These data suggest that SRIF inhibits GRF-provoked GH release by reducing the ability of the cAMP-protein kinase A but not of the calcium or protein kinase C intracellular message pathways to stimulate GH release.
AuthorsD J Donoghue, C G Scanes
JournalGeneral and comparative endocrinology (Gen Comp Endocrinol) Vol. 81 Issue 1 Pg. 113-9 (Jan 1991) ISSN: 0016-6480 [Print] United States
PMID1709126 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
Chemical References
  • Diglycerides
  • Phorbol Esters
  • 1,2-dioctanoylglycerol
  • Somatostatin
  • Growth Hormone
  • Growth Hormone-Releasing Hormone
  • Cyclic AMP
  • Protein Kinases
  • Adenylyl Cyclases
  • 1-Methyl-3-isobutylxanthine
Topics
  • 1-Methyl-3-isobutylxanthine (pharmacology)
  • Adenylyl Cyclases (metabolism)
  • Animals
  • Cells, Cultured
  • Chickens (physiology)
  • Cyclic AMP (analogs & derivatives)
  • Diglycerides (pharmacology)
  • Growth Hormone (metabolism)
  • Growth Hormone-Releasing Hormone (pharmacology)
  • Male
  • Phorbol Esters (pharmacology)
  • Pituitary Gland, Anterior (drug effects, physiology)
  • Protein Kinases (metabolism)
  • Somatostatin (pharmacology)

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