Large bowel carcinoma in strain-2 guinea pigs by intrarectal instillation of N-methyl-N'-nitro-n-nitrosoguanidine.

Intrarectal instillation of 0.5 ml of a 0.125% solution of N-methyl-N'-nitro-N-nitrosoguanidine twice weekly for 53 weeks to female inbred strain-2 guinea pigs induced multiple large bowel adenocarcinomas in 13 of 15 animals in 52 to 85 weeks. The lesions were plaque-shaped in small tumors and infiltrative or constrictive in large advanced tumors. The neoplasms showed histological features in varied grades of differentiation and invasiveness similar to those of human cases. These findings distinquished them from large bowel cancers chemically induced in rats and mice.