Colon tissue implanted into the glandular stomach in rats lack susceptibility to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) carcinogenesis

: The present study was undertaken to determine the response of colon mucosa implanted into the fundus of stomach in 6-week old male F344 rats to oral administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Samples of colonic tissue about 8 mm in diameter were obtained from various colon sites and surgically implanted into the anterior wall of the fundus by isografting. MNNG was chronically administered at a concentration of 100 mg/l in the drinking water for 16 weeks starting 4 weeks after the operation and the grafted colon mucosa was examined at 12 months after the operation. Control rats received a sham-operation and the same amount of MNNG. In the MNNG administered groups, only one adenoma containing Paneth cells was noted in the implanted colon tissue whereas over 40% incidence of gastric tumors was observed in the pyloric mucosa. In the operated rats not given MNNG no gastric tumors were observed in either the grafted site or the pylorus.