Genetic control of sensitivity of rats to gastrocarcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine.

The administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in drinking water induces tumours, mainly adenocarcinomas in the glandular stomach of rats. The sensitivities of different strains of rats to gastrocarcinogenesis induced by MNNG vary: Wistar and ACI strains are sensitive, whereas the Buffalo strain is resistant. Genetic analyses were made on the induction of gastric tumous by MNNG in the ACI and Buffalo strains and their F1 and F2 hybrids. Rats of both sexes, 7-9 weeks old, were given 83 micrograms of MNNG/ml of drinking water for 32 weeks and sacrificed in experimental week 72. The incidences of gastric tumours were as follows: ACI strain, male 80%, female 63%; Buffalo strain, male 29%, female 6%; F1 hybrid, male 35%, female 9%; F2 hybrid, male 65%, female 29%. There were no significant differences in the sensitivities of Buffalo X ACI F1 and ACI X Buffalo F1, or of Buffalo X ACI F2 and ACI X Buffalo F2. These results show that the gene(s) controlling resistance to MNNG is autosomal in the Buffalo strain and is inherited dominantly by F1 and F2 hybrids. In both strains and their hybrids, the incidence of gastric tumours was higher in males than in females.