Hepatic aldehyde and alcohol dehydrogenases in alcohol-preferring and alcohol-avoiding rat lines

The alcohol-avoiding ANA (Alko, Non-Alcohol) and alcohol-preferring AA (Alko, Alcohol) rat lines are known to differ in their acetaldehyde metabolism and were originally found to differ in hepatic alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activities in the 1970s. At the beginning of the 1980s, these rat lines were revitalized and some previously found line differences were lost. Thus, the purpose of this study was to determine whether these enzymatic line differences still exist and, if so, to study them further at the isoenzyme level. ADH and ALDH activities were measured from liver homogenates and different subcellular fractions of the rats. The ANA rats were found to have lower hepatic ALDH and higher ADH activities than AA rats, in accordance with the previous study. The line difference in ALDH activity was observed in all fractions, but was more apparent with millimolar than micromolar substrate concentrations and generally more pronounced in females than in males. The line difference in the microsomal ALDH activity was found to be quantitative, and it seemed to concern both microsomal ALDH isoenzymes. A qualitative line difference concerning mitochondrial high Km ALDH isoenzyme was found, and three different cytosolic ALDH isoenzyme patterns were observed, the frequencies of which were found to be different in the two lines. In conclusion, the results of the present study support the assumption that line differences in hepatic ADH and ALDH activities may be relevant to the acetaldehyde accumulation and the particularly low ethanol consumption of the ANA rats.