The Role of Acetaldehyde in the Pathogenesis of Acute Alcoholic Pancreatitis

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Abstract
Acetaldehyde (AA), the first product of ethanol metabolism, has been suggested as an important mediator in alcoholic pancreatitis, but experimental evidence has not been convincing. Prior work using the isolated perfused canine pancreas preparation has suggested that toxic oxygen metabolites generated by xanthine oxidase (XO) may mediate the early injury in pancreatitis. Xanthine oxidase is capable of oxidizing AA, and during this oxidation free radicals are released. The hypothesis that acute alcoholic pancreatitis may be initiated by AA in the presence of active XO (converted from xanthine dehydrogenase [XD]) was tested in the authors' experimental preparation by converting XD to XO by a period of ischemia, and infusing AA. Control preparations remained normal throughout the 4-hour perfusion (weight gain, 7 ± 4 g; amylase activity, 1162 ± 202 U/dL). One hour of ischemia, or infusion of AA at 25 mg/hr or at 50 mg/hr without ischemia did not induce changes in the preparation. Acetaldehyde at 250 mg/hr induced minimal edema and weight gain (16 ± 4 g; p < 0.05), but not significant hyperamylasemia. Changes also were not observed when 1-hour ischemia was followed by a bolus of ethanol (1.5 g) or sodium acetate (3.0 g), or by infusion of 25 mg/hr of AA. One hour of ischemia followed by infusion of AA at 50 mg/hr or at 250 mg/hr induced edema, hemorrhage, weight gain (22 ± 7 g [p < 0.05] and 26 ± 17 g [p < 0.05)) and hyperamylasemia (2249 ± 1034 U/dL [p < 0.05] and 2602 ± 1412 U/dL [p < 0.05]). Moreover infusion of AA at 250 mg/hr after 2 hours of ischemia potentiated the weight gain (62 ± 20 g versus 30 ± 14 g [p < 0.051), but not the hyperamylasemia (3404 ± 589 U/dL versus 2862 ± 1525 U/dL) as compared with 2 hours of ischemia alone. Pancreatitis induced by 1 hour of ischemia followed by AA at 50 mg/hr could be inhibited by pretreatment with the free radical scavengers superoxide dismutase and cat-alase and ameliorated with the XO inhibitor allopurinol. The authors conclude that AA, in the presence of active XO, can initiate acute pancreatitis in the isolated canine pancreas preparation and may be important in the initiation of acute alcoholic pancreatitis in man. Toxic oxygen metabolites appear to play an important intermediary role.