THE METABOLISM OF URETHANE AND RELATED COMPOUNDS

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Abstract
Urethane is metabolized in the rat, rabbit and man by a process of N-hydroxylation. This occurs to a smaller extent when methyl, n-propyl and n-butyl carbamates are administered to the rat and rabbit. Other metabolites which have been detected in urine of animals dosed with urethane and N-hydroxy-urethane are ethylmercapturic acid, ethylmercapturic acid sulfoxide and N-acetyl-S-carbethoxycysteine. Substances which appear to be S-ethylglutathione and S-ethylglutathione sulfoxide have been detected in the bile of rats dosed with urethane or N-hydroxyurethane. Methyl, ethyl, n-propyl and n-butyl N-hydroxycarbamates are excreted unchanged in the urine of rats dose with these compounds to extents depending on the dose administered. Animals dosed with methyl, ethyl, n-propyl or n-butyl carbamate or the corresponding N-hydroxy-carbamate excrete the corresponding carbamate and N-hydroxycarba-mate in the urine. Methyl, n-propyl and n-butyl carbamates and N-hydroxycarbamates are excreted more slowly than are urethane and N-hydroxyurethane. The probable role of N-hydroxyurethane and the processes of alkylation and carbethoxylation, and of hydroxylamine, nitroxyl and hyponitrous acid in carcinogenesis and chemotherapy with urethane, have been discussed.