CARCINOGENESIS INDUCED BY A SINGLE ADMINISTRATION OF 1,2-DIETHYLHYDRAZINE IN FEMALE RATS OF VARIOUS AGES

Three- or fourteen-month-old female L10 rats were exposed to a single intravenous injection of 1,2-diethylhydrazine (SDEH) at 150 mg/kg of body weight. At the 95th week after carcinogen treatment when the experiment was stopped, 30.7 % and 4.5 % of rats from the younger and older groups survived, respectively. Total tumor incidences were 68.8% and 84.6%, respectively, in rats treated with SDEH at the age of 3 or 14 months vs. 18.2% and 34.5% in corresponding young and old controls (P < 0.01). Leukemias, thyroid adenomas, uterine tumors and mammary malignancies developed more frequently in animals exposed to carcinogens than in control groups. No age-related differences in tumor incidence or localization between rats exposed to SDEH at various ages were observed, but tumors developed earlier in older groups than in younger groups. The results supported the suggestion that the accumulation of initiated cells in some tissues during natural aging is a cause of the age-related increase in cancer incidence.