Effect of Ethanol and Fructose on Galactose Elimination in Rat

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Abstract
The elimination rate of galactose was determined in intact 200 g rats by intravenous infusion of galactose during simultaneous infusion of ethanol (arterial ethanol concentrations about 7 mmol/l) or fructose (arterial fructose concentrations about 6 mmol/l). The galactose elimination capacity, defined as the elimination rate at blood galactose concentrations between 2 and 7 mmol/l, during ethanol infusion was, on the average, 80 μmol/h per whole animal, or two-thirds the value observed in comparable experiments without ethanol. Fructose did not change the galactose elimination capacity. The galactose elimination during ethanol infusion could be described by Michaëlis-Menten kinetics. The calculated Vmax was significantly lower than that obtained in experiments without ethanol. The pattern of the metabolites observed in liver tissue is compatible with an inhibitory effect of ethanol on UDP-glucose-4-epimerase, but with the phosphorylation of galactose by galactokinase as the rate-limiting step, inhibited by accumulation of galactose-1-phosphate. The galactose-1-phosphate concentration observed indicates a considerably smaller Ki for the inhibition of galactokinase by galactose-1-phosphate towards galactose than that observed by in vitro studies.

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