Rate determining factors of ethanol oxidation in hepatocytes from starved and fed rats: effect of acetaldehyde concentration on the rate of NADH oxidation catalyzed by alcohol dehydrogenase.

Rates of reduction of acetaldehyde and pyruvate catalyzed by alcohol dehydrogenase and lactate dehydrogenase have been estimated in isolated hepatocytes from rats metabolizing ethanol and [2-3H]lactate. The concentration of the substrates of the two dehydrogenases were varied by addition of fructose and cyanamide. Calculation of the rates are based on the detritiation pattern of lactate and the labelling pattern of ethanol and glucose. The rate of acetaldehyde reduction increased with the concentration of acetaldehyde and ranged from 1-20 mumol/min ml cells. Net ethanol oxidation was decreased only under conditions with a high rate of reduction of acetaldehyde. The results suggest that the rate of net ethanol oxidation is determined by the activity of acetaldehyde dehydrogenase relative to that of alcohol dehydrogenase.