A pharmacokinetic study of ethanol inhibition of micronuclei induction by urethane in mouse bone marrow erythrocytes

Abstract

Urethane (ethyl carbamate) is a genotoxic carcinogen in fermented products and alcoholic beverages. The genotoxicity of urethane requires metabolic activation. Metabolism of urethane is mediated by multiple pathways, and ethanol is known to inhibit the esterase hydrolysis pathway of urethane, which accounts for over 95% of urethane metabolism. This report shows that ethanol also inhibits the induction of micronuclei by urethane in mouse bone marrow erythrocytes, presumably by inhibiting the minor pathway that generates genotoxic metabolite(s). In this study, male CD-1 mice were administered urethane, ethanol, or urethane co-administered with increasing amounts of ethanol in single intraperitoneal injections. Bone marrow polychromatic erythrocytes (PCE) obtained 24 h after injection were scored for micronuclei. The dose of urethane was 1000 mg/kg, and the doses of ethanol were 0, 625, 1250, 2000, 2250, 3000 and 3500 mg/kg. The blood ethanol level at each dose was determined. Two pharmacokinetic parameters, C max and AUC, were estimated for each dose. The observed C max of ethanol at doses of 1250, 2000, 2250, 2500, 3000 and 3500 mg/kg were 1.39, 2.84, 3.15, 3.69, 4.13 and 4.76 mg/ml, with AUCs of 1.37, 4.84, 5.88, 7.28, 10.76 and 13.51 mg·h/ml, respectively. Urethane treatment alone markedly increased the micronucleus frequency from 0.1% in the vehicle control to 2.47%. This magnitude of increase was suppressed when urethane was co-administered with ethanol at ethanol doses of 2500 mg/kg and above. At 2500, 3000 and 3500 mg/kg, the micronucleus frequencies reduced from 2.47% to 0.9, 0.44 and 0.28%, respectively. This study shows that ethanol inhibits the induction of micronuclei by urethane.