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Effects of protein kinase C and cytosolic Ca 2+ on exocytosis in the isolated perfused rat liver
Author(s) -
Bruck Rafael,
Nathanson Michael H.,
Roelofsen Han,
Boyer James L.
Publication year - 1994
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.1840200436
Subject(s) - horseradish peroxidase , exocytosis , protein kinase c , ionomycin , protein kinase a , hepatocyte , cytosol , chemistry , endocrinology , medicine , biochemistry , biology , kinase , intracellular , secretion , enzyme , in vitro
Both protein kinase C and cytosolic Ca 2+ are involved in the regulation of exocytosis in a number of cell types. However, the relative importance of each of these for apical exocytosis in the hepatocyte is unknown. To investigate this, we studied the effects of protein kinase C and Ca 2+ agonists on horseradish peroxidase excretion in the isolated perfused rat liver. Vasopressin increased both horseradish peroxidase concentration and net horseradish peroxidase excretion in bile, and these effects were abolished by the protein kinase C inhibitor H‐7. The protein kinase C activator phorbol dibutyrate also increased both net excretion and the concentration of biliary horseradish peroxidase. In contrast, the Ca 2+ ionophore A23187 and the Ca 2+ mobilizing agent 2′,5′‐di ( tert butyl)‐1,4,‐benzohydroquinone both had minimal effects on horseradish peroxidase concentration and inhibited the rate of horseradish peroxidase excretion. These results suggest that protein kinase C stimulates apical exocytosis in the hepatocyte, whereas increased Ca i 2+ per se does not influence exocytosis and inhibits excretion only transiently by reducing bile flow. (Hepatology 1994;20:1032‐1040).