Acetaldehyde metabolism by isolated hepatic mitochondria from rats consuming different amounts of ethanol

We have previously reported that in rats, ethanol intake as low as 4 g/kg per day induced mitochondrial alterations, detected by a decrease in mitochondrial O2 uptake supported by substrates entering at the three sites of coupled phosphorylation. Since it has been reported that acetaldehyde oxidation occurs mainly inside the mitochondria, linked to the respiration chain, the effect of daily previous administration of low doses of ethanol during a month, on the acetaldehyde oxidation rate by intact rat liver mitochondria was studied. Determination of acetaldehyde oxidation rate and O2 uptake accompanying acetaldehyde removal by liver mitochondria indicates that the mean value of these parameters studied in rats consuming low amount of ethanol (0.5-3.0 g/kg per day) was significantly higher than that of controls drinking only water (P less than 0.001, in state 3, and P less than 0.05, in state 4). This enhancing effect of ethanol cannot be ascribed to an uncoupling of oxidative phosphorylation and also not to a change in aldehyde dehydrogenase activity which was measured in disrupted mitochondria. On the other hand, high ethanol consumption (4-7 g/kg per day), which alters mitochondrial function, did not decrease mitochondrial acetaldehyde oxidation, as compared to rats drinking water only. This result differs from the decrease induced by higher levels of previous ethanol intake (12-14 g/kg per day) as reported by several authors, showing that possibly this effect is dose dependent.