The effects of zinc on first-pass metabolism (FPM) of ethanol and gastric and hepatic alcohol dehydrogenase (ADH) activities have been investigated in two groups of male Wistar rats fed a liquid ethanol diet with normal zinc content (7.6 mg/liter), or zinc supplemented (76 mg/liter), for 21 days, and in two pair-fed groups receiving the same diets without ethanol. Alcoholic rats with normal dietary zinc had lower FPM (1.64 +/- 0.25 vs. 2.43 +/- 0.20 mM x hr, p < 0.05) and gastric ADH activity (184 +/- 7 vs. 335 +/- 41 micromol/min/mg protein, p < 0.01) than control rats. Zinc supplementation did not produce any change in FPM or in gastric ADH activity in control rats. By contrast, in alcoholic rats, the zinc supplement increased gastric ADH activity (247 +/- 31 vs. 184 +/- 7 micromol/min/mg protein, p < 0.05) and decreased the areas under the curve of blood ethanol concentrations after the intragastric administration of 0.25 g/kg of body weight of ethanol (0.78 +/- 0.07 vs. 1.71 +/- 0.24 mM x hr, p < 0.05), thereby increasing the FPM. In conclusion, in alcohol-fed rats, the administration of zinc supplements restores gastric ADH activity and improves the FPM of ethanol. These effects may be one of the mechanisms in which zinc has a beneficial role in preventing the development of alcoholic hepatic lesions.