Open AccessIsotope Effects and Hydrogen Transfer during Simultaneous Metabolism of Ethanol and Cyclohexanone in Rats
Author(s) -
Cronholm Tomas
Publication year - 1974
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1974.tb03399.x
Subject(s) - chemistry , alcohol dehydrogenase , ethanol , kinetic isotope effect , ethanol metabolism , alcohol , metabolism , tritium , metabolite , deuterium , biochemistry , quantum mechanics , nuclear physics , physics
The metabolism of ethanol in vivo was studied by measurements of tritium isotope effects and extent of hydrogen transfer from ethanol to a reducible substrate of liver alcohol dehydrogenase. The specific radioactivity of ethanol in bile increased by a factor of two in 6–8 h following administration of [1‐ 3 H]ethanol, 11 mmol/kg. This indicates a tritium isotope effect of about 1.6 on the association of [1‐ 3 H]ethanol to the alcohol dehydrogenase‐NAD complex or on the rate of conversion of the ternary complex. Cyclohexanone was used as the reducible substrate of liver alcohol dehydrogenase. The major metabolite in bile was cyclohexyl glucuronide. During the simultaneous metabolism of [1,1 ‐ 2 H 2 ]‐ethanol with a deuterium excess of 95 atoms % the cyclohexanol formed had a deuterium excess of about 65 atoms %. This dilution cannot be explained by the isotope effect and is most likely due to the reversible dissociation of the enzyme‐NADH complex resulting in exchange with a less‐labelled free‐NADH pool. Ethanol metabolism increased the rate of cyclohexanone elimination, probably by increasing the concentration of alcohol dehydrogenase‐NADH complex. A large dose of cyclohexanone decreased the ethanol‐elimination rate, possible due to competitive inhibition.