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 mu cosa 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 con centration of 100 mg/l in the drinking water for 16 weeks starting 4 w eeks 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 tiss ue whereas over 40% incidence of gastric tumors was observed in the py loric mucosa. In the operated rats not given MNNG no gastric tumors we re observed in either the grafted site or the pylorus.