Effect of age and strain on N-methyl-N'-nitro-N-nitrosoguanidine tumorigenesis in ACI and Wistar Furth rats.

N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) dissolved in distilled water (5 g/l) was administered orally once by gastric tube at a dose of 0.25 ml/10 g body weight to 5-day-old or 28-day-old Wistar Furth (W/Fu) or ACI rats. Gastric tumors in the glandular stomach were found in 58% of 5-day-old ACI rats, but none were found in the rest of the groups. Forestomach tumors were found in both strains of rats at both age groups with incidences of 68-100%. Lung tumors were induced in 64% of 5-day-old and 6% of 28-day-old W/Fu rats, but not in ACI rats. Besides the tumors, a high frequency of hepatic cysts was also noted in ACI rats. Intestinal metaplastic foci with alkaline phosphatase activity were found in the group of 5-day-old ACI rats and none in the rest of the groups. The results showed that the incidences and the locations of tumors in rats induced by MNNG are greatly influenced by both strain and age.