Sequential studies on the histopathogenesis of gastric carcinoma in rats by a weak gastric carcinogen, N-propyl-N'-nitro-N-nitrosoguanidine.

Sequential studies were made on the histopathologic changes in the glandular stomach of rats induced by a weak carcinogen. N-propyl-N'-nitro-N-nitrosoguanidine (PNNG). Fiftyfour rats were given 100 micrograms/ml of PNNG in their drinking water for 44 weeks, and then normal tap water until the end of the experiment. Rats were killed at intervals between week 1 and week 88. No marked atrophy or ulceration of the mucosa was found between week 1 and the end of the experiment. Focal intestinal metaplasia was found in week 19 and its incidence increased during the experiment. Adenocarcinoma in situ with extreme cellular atypia was found in mucosa with a normal appearance in week 67. An adenocarcinoma invading the submucosa was found in week 69, and one invading the serosa in week 88. All these pathological lesions were found on the anal side of the pyloric region. No pathologic changes were found in the fundic region. The sequential changes of the mucosa of the glandular stomach induced by this weak gastric carcinogen, PNNG, were very different from those induced by the potent gastric carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Gastric carcinoma induced by PNNG seems to be more similar to human gastric cancer than that induced by MNNG.