Pathways of Ethanol Metabolism in the Rat

Ethanol metabolism at endogenous concentrations in the rat is still not precisely defined, primarily because of the difficulty in comparing ethanol and acetate metabolism directly. To facilitate this comparison, an experimental design was developed which utilized labeling ratios. With the intact rat, results from this approach suggest that the labeling of precursor acetyl-CoA for fatty acid and cholesterol biosynthesis, as well as the oxidation of ethanol via the tricarboxylic acid cycle, is consistent with the conversion of ethanol to acetyl-CoA, providing acetate and ethanol are taken up unequally by the various tissues. An in-vitro study of seven tissues demonstrates this unequal uptake of ethanol and acetate, while the labeling ratios indicate no difference between ethanol-C14 and acetate-C14 with respect to the metabolism of these two compounds to carbon dioxide. These results, and results from perfusion studies, are consistent with the major pathway for ethanol metabolism proceeding via acetate.