Tumour formation in mice by urethane administered with related carbamates

A tumour initiating dose of ethyl carbamate was administered to mice by subcutaneous injection together with a dose of one of the homologous esters or an ethyl N-alkyl derivative. The homologues used were the methyl, n-propyl and n-butyl esters, and the derivatives were the N-methyl, N-ethyl and N-n-propyl ethyl esters. The mice were then given promoting treatment with croton oil for 28 weeks.Neither the homologous esters nor the N-substituted derivatives of ethyl carbamate had any influence on the yield of tumours in the skin, lung, or liver. However, increasing the dose of ethyl carbamate increased the yields of tumours.