Alcohol-induced mitochondrial changes in the liver.

The chronic ingestion of ethanol results in liver-cell damage, and characteristic features of this injury are the marked alterations in both the functions and morphology of the mitochondria. Morphologically, the changes observed in human alcoholics and experimental animals appear similar. Bizarrely shaped mitochondria and megamitochondria are detected at the fatty liver stage and persist as the disease progresses. As yet, however, no correlation has been found between the severity of these morphological changes and the development of cirrhosis. Analysis of the mitochondrial membranes indicates that ethanol consumption produces changes in both the protein and lipid composition of the membrane. Profound decreases in the components of the respiratory chain have been detected, and these changes are associated with marked depressions in the activity of NAD+-linked dehydrogenases, cytochrome oxidase, and the ATP synthetase complex. On the other hand, no consistent pattern has emerged as to the effect of chronic ethanol consumption on the composition of the membrane phospholipids. Many of the changes appear to be dependent on the sex of the animal, the dietary status, and the duration of ethanol intake, and are suggestive of changes in fatty acid desaturase activity. Mitochondria isolated from ethanol-fed rats displayed impaired respiration and a lowered steady-state rate of ATP synthesis. Whether or not these functional changes are directly related to alterations in the physical properties of the membranes remains to be resolved. This marked depression of respiratory functions in isolated mitochondria was not reflected by a significant decrease in O2 consumption by the livers of ethanol-fed animals.