Ethanol-acetaldehyde exchange in vivo and in isolated hepatocytes.

Extensive exchange of hydrogen atoms at C-1 between ethanol molecules has been observed in whole rats and isolated rat hepatocytes with the aid of differently deuterium-labelled ethanols. Thus, acetaldehyde molecules are reduced to ethanol after dissociation from the enzyme. The exchange was specific for the 1-pro-R hydrogen. The results indicate that in addition to the reoxidation of NADH, both oxidation of acetaldehyde and dissociation of NADH from alcohol dehydrogenase contribute to the determination of the rate of ethanol elimination. This was found to be true even when ethanol elimination was partly inhibited by 4-methylpyrazole, which shows that significant concentrations of acetaldehyde are present even when the rate of production is low.