The effects of age on tumour induction in C57BL mice using 1,2-dimethylhydrazine.

Adult (6-8 months) and aged (22-24 months) male C57BL/Icrf at mice were given 8.25 or 12.25 mg 1,2-dimethylhydrazine(DMH)/kg weekly s.c. and groups of 4 animals autopsied after 8, 12, 16, 20, 24 or 36 treatments. No age difference was found in the development or appearance of large bowel tumours. Abnormal glands, not found less than 150 mg DMH/kg, preceded polyps and adenocarcinomas which occurred greater than 300 mg/kg. Treated mice showed hepatic cell damage, and biliary hyperplasia developed after 20 weeks. Seven haemangiosarcomas of the urogenital tract and 2 perianal carcinomas occurred in 11 adult mice surviving greater than 24 weeks at 12.5 mg/kg: no haemangiosarcomas but 1 perianal carcinoma occurred in 4 remaining mice in the equivalent aged group. Ileal amyloid was present in the old mice.