Kinetics and Control of Alcohol Oxidation in Rats
The rates of oxidation of ethanol and isopropanol by purified rat liver alcohol dehydrogenase were determined in vitro and compared to the rates of metabolism in vivo in order to estimate the extent to which alcohol dehydrogenase activity limits ethanol metabolism. The metabolism of isopropanol and isopropanol-d7 (CD3CDOHCD3) was examined by measuring blood alcohol and acetone levels at various times and apparently proceeds by an irreversible, enzyme-catalyzed pathway: isopropanol → acetone → an unidentified metabolite. The kinetic constants for the metabolism were computed from simultaneous fits to the appropriate differential equations using a nonlinear least-squares program. The relative rates of oxidation of the alcohols, ethanol:isopropanol:isopropanol-d7, at 25 mM were 9.6: 2.3: 1.0 in vitro and 4.1: 2.4: 1.0 in vivo. Since the ratio of rates for isopropanol is about the same in vitro and in vivo it appears that alcohol dehydrogenase activity is the predominant rate-limiting factor in isopropanol metabolism. The relatively slower rate of ethanol oxidation in vivo as compared to in vitro suggests that liver alcohol dehydrogenase is partially (about 40%) limiting for ethanol metabolism.
KeywordsAlcohol Dehydrogenase Ethanol Oxidation Alcohol Oxidation Ethanol Metabolism Alcohol Dehydrogenase Activity
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- Brooks, R. L. and Shore, J. D., 1971, Effect of substrate structure on the rate of the catalytic step in the liver alcohol dehydrogenase mechanism, Biochemistry 10: 3855–3858.Google Scholar
- Cleland, W. W., 1967, The statistical analysis of enzyme kinetic data, in: “Advances in Enzymology,” F. F. Nord, ed., Wiley-Interscience, New York.Google Scholar
- Cornell, N. W., Crow, K. E., Leadbetter, M. G. and Veech, R. L., 1978, Kinetics of alcohol dehydrogenase and the rate of ethanol metabolism in the rat in vivo, Fed. Proc. 37:1605; or Rate determining factors for ethanol oxidation in rats in vivo and in isolated rat hepatocytes, in: “Alcohol and Nutrition,” T. K. Li, S. Schenker and L. Lumeng, eds., DREW Pub. No. (ADM) 79–780.Google Scholar
- Crow, K. E., Cornell, N. W. and Veech, R. L., 1977, The role of alcohol dehydrogenase in governing rates of ethanol metabolism in rats, in: “Alcohol and Aldehyde Metabolizing Systems,” R. G. Thurman, J. R. Williamson, H. Drott and B. Chance, eds., Vol. III, Academic Press, New York.Google Scholar
- Cershman, H. and Abeles, R. H., 1973, Deuterium isotope effects in the oxidation of alcohols in vitro and in vivo Arch. Biochem. Biophys. 15:659–674.Google Scholar
- Lester, D. and Benson, G. D., 1970, Alcohol oxidation in rats inhibited by pyrazole, oximes and amides, Science 169: 282–284.Google Scholar
- Lumeng, L., Bosron, W. F. and Li, T. K., 1979, Quantitative correlation of ethanol elimination rates in vivo with liver alcohol dehydrogenase activities in fed, fasted and food restricted rats, Biochem. Pharmacol. 28:154 7–1551.Google Scholar
- Markovic, O., Theorell, H. and Rao, S 1971, Rat liver alcohol dehydrogenase. Purification and properties, Acta Chem. Scand. 25:195–205.Google Scholar
- Nordmann, R., Ribiere, C., Rouach, H., Beauge, F., Giudicelli, Y., and Nordmann, J., 1973, Metabolic pathways involved in the oxidation of isopropanol into acetone by the intact rat, Life Sci., 13: 919–932.Google Scholar
- Plapp, B. V., 1970, Enhancement of the activity of horse liver alcohol dehydrogenase by modification of amino groups at the active sites, J. Biol. Chem. 245:1727–1735.Google Scholar
- Plapp, B. V., 1975, Rate-limiting steps in ethanol metabolism and approaches to changing these rates biochemically, in: “Biochemical Pharmacology of Ethanol,” E. Majchrowicz, ed., Plenum Press, New York.Google Scholar
- Roach, M. K. and Creaven, P. J., 1968, A micro-method for the determination of acetaldehyde and ethanol in blood, Clin. Chin. Acta 2]:275.Google Scholar