Liver and lung tumors in mice exposed at birth to 4-dimethylaminoazobenzene or its 2-methyl or 3'-methyl derivatives.

Male and Female Swiss mice received, by subcutaneous injection on each of the First 5 days of life, 200 mg 4-dimethylaminoazobenzene (DAB), 2-methyl-4-dimethylaminoazobenzene (2-methyl-DAB), or 3'-methyl-4-dimethylaminoazobenzene (3'-methyl-DAB). A control group was similarly treated with the vehicle, 0.02 ml arachis oil. Between 50 and 56 mice in each group survived until the experiment was terminated 1 year later. The incidence of liver cell adenomas (benign hepatomas) was significantly higher in male mice given any 1 of the 3 test compounds (63-92%) than in the control males given arachis oil only (10%), and the incidence in males given DAB (92%) was significantly higher than in males given 2-methyl-DAB (67%) cm' 3'-methyl-DAB (63%). None of the treatments significantly increased the incidence of liver tumors in female mice. The incidence of lung tumors in control males was 10% and in control Females 4%. DAB itself had little or no effect on the incidence of lung tumors (a, = 8%, 9 = 16%), but 3'-methyl-DAB significantly increased lung tumor incidence in both sexes (a, = 34%, 9 5070) and 2-methylDAB did so in Females (cr = 11%, 9 = 42%). The interpretation of these findings is discussed in the light of the results of experiments based on the exposure of partially hepatectomized adult rats to the same compounds, the results of studies on germfree mice, and of postulated metabolic pathways.—J Nat Cancer Inst 47: 593-601,1971.