[Effect of age on induction of intestinal tumors in mice by 1,2-dimethylhydrazine]

1,2-Dimethylhydrazine was administered subcutaneously in a dose of 8 mg/kg bw to 2-, 8- and 12-month-old female CBA mice for 25 weeks. The animals were serially killed 26-35 weeks after the beginning of treatment. The incidence of colon tumors in 2-month-old mice was always significantly lower (P less than 0.001) than in 8- or 12-month-old mice. The incidence of tumors with invasive growth in 12-month-old mice was significantly higher (P less than 0.05) than in 8-month-old mice. Mathematical evaluation allowed the conclusion about the 1.8-fold shortening of the colon tumor latency period in old mice as compared to the young mice.