Ethanol-induced changes in hepatic free radical defense mechanisms and fatty-acid composition in the miniature pig



In the miniature pig, ethanol consumption has been reported to induce alterations in hepatic antioxidant defense capacity, which could result in increased risk of peroxidative damage. However, ethanol may also induce changes in membrane fatty acid composition, which could reduce the risk of peroxidative damage. This study examined lipid peroxidation, antioxidant defense and fatty acid composition in livers from miniature pigs fed ethanol in diets containing 12% of their calories as fat for 20 mo. After 12 and 20 mo of feeding, ethanol-fed pigs had higher hepatic manganese–superoxide dismutase activity, lower hepatic copper concentrations and low hepatic copperzinc–superoxide dismutase and glutathione peroxidase activities compared with controls. Lipid peroxidation as assessed by thiobarbituric acid reacting substance assay was lower in liver homogenate and mitochondrial and microsomal fractions from ethanol-fed pigs than in controls. The percentage contribution of highly unsaturated fatty acids to total fatty acids in liver homogenates (after 12 mo of feeding) and microsome fractions (after 20 mo of feeding) was lower in the ethanol-fed pigs than in the controls, resulting in a lower peroxidizability index. Ethanol-fed pigs had minimal or no hepatic damage as assessed by histological methods. We suggest that the relative resistance of microsomes to lipid peroxidation is due to the lower peroxidizability index in the ethanol-fed pigs and may account in part for the absence of significant histopathological findings after 20 mo of ethanol feeding. (HEPATOLOGY 1991;13:1185–1192.)