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 indistilledwater (5 g/1) was administered orally once by gastrictube ata dose of 0.25 ml/10 g body weight to 5-day-old or 28-day-oldWistar Furth (W/Fu) or ACI rats. Gastric tumorsin the glandularstomach were found in 58% of 5-day-old ACI rats, but none werefound in the rest of the groups. Forestomach tumors were foundin both strains of rats at bothage groups with incidences of68–100%. Lung tumors wereinduced in 64% of 5-day-old and6% of 28-day-old W/Fu rats,but not in ACI rats. Besides thetumors, a high frequency of hepatic cysts was also noted inACI rats. Intestinal metaplastic foci with alkaline phosphataseactivity were foundin the group of 5-day-old ACI rats and nonein the rest ofthe groups. The results showed that the incidencesand thelocations of tumors in rats induced by MNNG are greatlyinfluencedby both strain and age.