Ethanol modifies the actin cytoskeleton in rat pancreatic acinar cells--comparison with effects of CCK.
BACKGROUND
One of the early events leading to alcoholic pancreatitis seems to be the effect of ethanol on stimulus-secretion coupling. This study examines ethanol-induced modifications of filamentous actin (F-actin) content and localization in acini, the resulting alpha-amylase secretion and the role of protein kinase C (PKC) activity in these processes.


METHODS
Freshly isolated acini were treated with different concentrations of ethanol or cholecystokinin octapeptide (CCK-8) for different periods. F-actin was localized by confocal laser scanning microscopy; its quantity was determined fluorometrically, and the alpha-amylase secretion was measured.


RESULTS
Ethanol caused F-actin reorganization resembling the effects of supramaximal CCK-8 stimulation and of direct PKC activation by phorbol-12-myristate-13-acetate. The polyphasic time course of the F-actin content also resembled that under supramaximal CCK-8 stimulation and was counteracted by inhibition of PKC. The PKC inhibitor bisindolylmaleimide I did not increase the ethanol- induced alpha-amylase secretion, but the suboptimally CCK-8-stimulated secretion via high-affinity receptors.


CONCLUSIONS
Ethanol, like supramaximal CCK-8 concentrations, inhibits acinar secretion by reorganization of the actin cytoskeleton via PKC activation. This effect is suggested to be mediated by low-affinity CCK-A receptors. Together with the ethanol-induced stimulation of early steps of stimulus-secretion coupling, this may be a pancreas-damaging mechanism resembling that in experimental hyperstimulation pancreatitis.
Siegmund
Eva
E
Institute of Clinical Chemistry and Pathobiochemistry, University of Rostock, Rostock, Germany. eva.siegmund@med.uni-rostock.de
Lüthen
Frank
F
Kunert
Johanna
J
Weber
Heike
H
D000199:Actins / Q000032:analysis*; D000818:Animals; D003599:Cytoskeleton / Q000737:chemistry* / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D010179:Pancreas / Q000201:enzymology / Q000648:ultrastructure*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D012844:Sincalide / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D000516:alpha-Amylases / Q000378:metabolism
D000199:Actins; D004791:Enzyme Inhibitors; D000431:Ethanol; D007770:L-Lactate Dehydrogenase; D011493:Protein Kinase C; D000516:alpha-Amylases; D012844:Sincalide; D013755:Tetradecanoylphorbol Acetate