Chronic ethanol consumption causes alterations in the structural integrityof mitochondrial DNA in aged rats

Chronic ethanol consumption adversely affects the respiratory activity of r at liver mitochondria, It causes increased cellular production of oxygen ra dical species and selectively decreases mitochondrial glutathione (GSH) lev els, Here we show, using Southern hybridization techniques on total rat gen omic DNA, that long-term (11-13 months) ethanol feeding, using the Lieber-D eCarli diet, results in a 36% (P <.05; n = 4) decrease in hepatic mitochond rial DNA (mtDNA) levels when compared with paired controls. UV quantitation of mtDNA isolated from hepatic mitochondria showed that chronic ethanol in take (11-13 months) causes a 44% (P <.01; n = 6) decrease in the amount of mtDNA per milligram of mitochondrial protein. No significant decline in mtD NA levels was seen in ethanol-fed animals maintained on the diet for 1 to 5 months. Ethanol feeding caused a 42% (P <.01; n = 4) and a 132% (P <.05; n = 3) increase in 8-hydroxydeoxyguanosine (8-OHdG) formation in mtDNA in an imals maintained on the diet for 3 to 6 months and 10 to 11 months, respect ively. In addition, agarose gel electrophoresis revealed a 49% increase (P <.05; n = 3) in mtDNA single-strand breaks (SSB) in animals fed ethanol for more than 1 year. These findings suggest that chronic ethanol consumption causes enhanced oxidative damage to mtDNA in older animals along with incre ased strand breakage, and that this results in its selective removal/ degra dation by mtDNA repair enzymes.