Effects of Partial Hepatectomy on Carcinogenicity, Metabolism, and Binding to DNA of Ethyl Carbamate

Male and female mice were given injections of ethyl carbamate at intervals after one-third or two-thirds hepatectomy. The incidence of hepatocellular tumors was increased after partial hepatectomy and correlated with both the number of cells synthesizing DNA at injection and the number of cells in mitosis. Partial hepatectomy did not affect the yields of lung tumors, liver hemangiomas, or the number and character of skin tumors if ethyl carbamate was followed by a promoting treatment with croton oil. More hepatocellular tumors occurred in males, but no sex differences in the numbers of liver hemangiomas, lung adenomas, or skin tumors were observed. The binding of an ethyl carbamate metabolite to liver DNA was fourteen times greater in males but the level of binding to lung or epidermal DNA showed no sex differences. Partial hepatectomy increased the binding to liver DNA in both sexes but did not alter the amount bound to lung or epidermal DNA. The rate of metabolism of ethyl carbamate was slower after partial hepatectomy, but this did not create a significant increase in the effective dose.