Effect of epinephrine on ethanol metabolism by isolated rat hepatocytes

Abstract

The effect of epinephrine on ethanol metabolism was determined in isolated rat hepatocytes. Epinephrine (10 μM) enhanced an initial rapid rate of ethanol elimination observed in the first 5 min. Thereafter, between 5 and 90 min, the rate of ethanol elimination was slower and not affected by epinephrine. Epinephrine resulted in higher acetaldehyde concentrations at 2 min, but not thereafter. Acetaldehyde production in the presence and absence of epinephrine was inhibited by 4-methylpyrazole, by a low free extracellular calcium concentration, and by the α 1-adrenergic blocker prazosin. Ethanol alone and epinephrine alone increased oxygen consumption, but the effects were not additive. The ethanol-induced decreases in the cytosolic NAD +/NADH and NADP +/NADPH ratios and in the mitochondrial NAD +/NADH ratio were delayed by the presence of epinephrine. An accelerated initial alcohol dehydrogenase activity sufficient to account for the rapid initial rate of ethanol elimination shown with epinephrine was demonstrated by coupling ethanol oxidation with lactaldehyde reduction, a system which increases the rate of dissociation of NADH from the enzyme and its oxidation back to NAD +. The findings in this study indicate that an increased reoxidation of NADH during ethanol oxidation by alcohol dehydrogenase is the basis for the rapid transient increase in ethanol elimination produced by epinephrine.