Activities of ethanol-metabolizing enzymes in liver diseases.

The activities of hepatic alcohol (ADH), aldehyde (ALDH), and lactate dehydrogenases were measured in 69 patients with various liver diseases (15 controls, 20 with alcoholic and 8 with non-alcoholic fatty liver, 13 with alcoholic cirrhosis, 2 with alcoholic hepatitis, 3 with cryptogenic and 3 with primary biliary cirrhosis, and 5 with acute or chronic hepatitis). The specific activities of all these enzymes were decreased in both alcoholic and non-alcoholic liver diseases. The activities of ADH and low-Km ALDH were significantly decreased both in alcoholic (ADH, 7.22 mU/mg protein, p less than 0.001; low-Km ALDH, 5.00 mU/mg protein, p less than 0.001) and in other liver diseases (ADH, 10.70 mU/mg protein, p less than 0.001; low-Km ALDH, 6.80 mU/mg protein, p less than 0.005) when compared with controls (ADH, 20.87 mU/mg protein; low-Km ALDH, 14.41 mU/mg protein). The hepatic protein content was significantly (p less than 0.001) increased in alcoholic fatty degeneration but not in alcoholic cirrhosis or other liver diseases. The results suggest that in man alcohol- and acetaldehyde-metabolizing enzymes are not induced by chronic alcohol consumption. On the contrary, the hepatic activities of these enzymes appeared to be lower in alcoholic than in non-alcoholic liver diseases. Consequently, in addition to liver injury alcohol may also directly affect the synthesis or breakdown of alcohol-metabolizing enzymes.