Gastric carcinoma developing in chronic gastric ulcer in the rat treated with N-methyl- N1-nitro- N-nitrosoguanidine

Abstract

The purpose of this experiment was to determine if chronic gastric ulcer in the rat is prediposed to tumor formation when exposed to a known gastric carcinogen. N-methyl- N 1-nitro- N-nitrosoguanidine (NG). Rats were subjected to a standard ulcer-producing operation. Treatment with oral NG (as drinking water) was continued for at least 40 weeks. Appropriate control groups underwent sham operation and/or were fed with tap water. The experiment terminated at 52 weeks. The results showed that significantly more tumors were found at the edge of a chronic ulcer or at the site of previous mucosal injury in the rats which had the ulcer-producing operation and fed with NG than controls ( P < 0.005). However, the number of tumors per rat stomach was the same when the rats were treated with NG whether an ulcer-producing operation or a sham operation was carried out. Furthermore, 18 52 rats in the group with ulcer-producing operation and NG had chronic ulcers without tumors. It is concluded that, in the rat, the presence of a chronic gastric ulcer is more likely to localize the development of a tumor to the ulcer or to the site of previous injury, but does not increase the overall incidence of gastric tumors.