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Insulin inhibits secretin‐induced ductal secretion by activation of PKC alpha and inhibition of PKA activity
Author(s) -
LeSage Gene D.,
Marucci Luca,
Alvaro Domenico,
Glaser Shan S.,
Benedetti Antonio,
Marzioni Marco,
Patel Tushar,
Francis Heather,
Phinizy Jo Lynne,
Alpini Gianfranco
Publication year - 2002
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1053/jhep.2002.35537
Subject(s) - medicine , endocrinology , cholangiocyte , insulin , secretin , protein kinase c , insulin oscillation , biology , secretion , chemistry , signal transduction , microbiology and biotechnology , insulin resistance
Insulin stimulates canalicular bile flow by interaction with hepatocytes. Insulin regulates the function of a number of epithelia through activation and membrane translocation of Ca 2+ ‐dependent PKC isoforms. No information exists regarding insulin regulation of ductal bile secretion. The aim of the study was to determine the role and mechanisms of action of insulin in the regulation of cholangiocyte secretion in BDL rats. We determined the subcellular localization of insulin receptor in cholangiocytes. We measured the effect of insulin on (1) secretin‐stimulated cAMP levels in cholangiocytes and duct expansion in intrahepatic bile duct units (IBDUs) in the absence or presence of BAPTA/AM, H7 or rottlerin and (2) bile flow. We evaluated (1) if insulin effects are associated with activation of PKC alpha and (2) if activation of PKC causes inhibition of secretin‐stimulated cAMP levels and PKA activity. We found insulin receptors only in the apical domain of cholangiocytes. Insulin inhibited secretin‐induced choleresis and secretin‐stimulated cholangiocyte cAMP levels. Insulin inhibited secretin‐induced secretion in IBDUs when applied at the basolateral membrane or microinjected into IBDU lumen. Insulin inhibitory effects on cholangiocyte secretion were blocked by BAPTA/AM and H7. Insulin induced activation of PKC alpha, which decreased secretin‐stimulated cAMP and PKA activity. In conclusion, insulin inhibited secretin‐induced ductal secretion of BDL rats through activation of PKC and inhibition of secretin‐stimulated cAMP and PKA activity. In conclusion, insulin counter‐regulates cholangiocyte secretory processes in the BDL model, which is characterized by cholangiocyte proliferation.