Further Studies on the 37 Kd Liver Protein–Acetaldehyde Adduct That Forms In Vivo During Chronic Alcohol Ingestion

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Abstract
We have previously reported the detection of a 37 kD liver protein–acetaldehyde adduct in rats fed alcohol chronically with the AIN'76 diet. It was surprising that only one liver protein–acetaldehyde adduct was found. In this report, we have tried to detect additional protein–acetaldehyde adducts by electroimmunotransblot with rabbit anti–hemocyanin–acetaldehyde adduct IgG and to further characterize the 37 kD liver protein–acetaldehyde adduct. Sensitivity of electroimmunotransblot increased 10–to 20–fold when alkaline phosphatase–linked antibody was used in place of horseradish peroxidase, but only one protein–acetaldehyde adduct band was detected in liver. Feeding rats the Lieber–DeCarli alcohol diet also did not produce more protein–acetaldehyde adduct bands in electroimmunotransblot. Addition of cyanamide, an aldehyde dehydrogenase inhibitor, to the AIN'76 alcohol diet greatly increased the intensity of the 37–kD protein–acetaldehyde adduct band on electroimmunotransblot but did not produce other bands. The 37 kD protein–acetaldehyde adduct decayed in vivo with a half–life of 4 days when alcohol was removed from the diet. The 37 kD protein–acetaldehyde adduct in liver is cytosolic. Its interaction with anti–hemocyanin–acetaldehyde adduct IgG was blocked by polylysine–acetaldehyde adduct and polytyrosine–acetaldehyde adduct. It could be removed by immunosorption with anti–hemocyanin–acetaldehyde adduct IgG–bound immunoresin. When immunoblotted with anti–alcohol dehydrogenase and anti–aldehyde dehydrogenase antibodies, the alcohol dehydrogenase and aldehyde dehydrogenase bands in liver of alcoholfed rats showed identical intensities before and after immunosorption. These data indicate that: (i) the 37 kD protein–acetaldehyde adduct is neither alcohol dehydrogenase nor aldehyde dehydrogenase; (ii) its interaction with anti–hemocyanin–acetaldehyde adduct IgG is by way of acetaldehyde adducts of ε– and/or α–amino groups; (iii) its formation and decay in liver in vivo are likely to depend on acetaldehyde concentration.