UTILIZATION OF NEWBORN MICE IN BIOASSAY OF CHEMICAL CARCINOGENS

Newborn ICR Swiss mice received a single maximum tolerated subcutaneous injection of the test chemicals. Six months later the lungs were examined and the mean number of adenomas and percentage of animals with adenomas were determined. A significant increase in mean number of adenomas was observed after urethan (1000 or 1500 mg/kg) and N-nitrosodiethylamine (50 mg/kg) treatment. Liver tumors were also observed after the N-nitrosodiethylamine treatment. Mean adenoma counts comparable to control values were observed after treatment with thiourea (2500 mg/kg), mesidine (250 mg/kg), aflatoxin (2.5 mg/kg), 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT, 15 g/kg), croton oil (0.5 ml/kg), dodecylbenzene (12.5 ml/kg), or dimethyl sulfoxide (6 ml/kg). The vehicle control incidence of lung adenomas, after saline or peanut oil injection, varied from 2 to 14%, and the mean number of adenomas was 0.02 to 0.14. The bioassay procedure appears to be negative to promoter substances. The effect of nitrogen mustard on lung adenoma incidence was reduced when the vehicle was peanut oil or tricaprylin. © 1969.