Long-term oral administration of NG is known to produce gastric carcinomas in dogs. This experiment was designed in order to investigate problems concerning the process of the gastric carcinomas. Adult dogs, weighing 7kg on the average, took about 300ml of 80μg/ml NG solution daily for 1, 2, 4, and 6 months, thereafter, they were sacrificed.
Histologically, adenocarcinoma tubulare and/or mucocellulare developed in the angular and cardiac portions of the stomach in one of 6-months group dogs. Many erosions and shallow ulcers, including healed scars, were observed as the preceding gastric mucosal damages. Favourite sites of these mucosal defects were on the antro-angular portion near the lesser curvature and on the cardiac portion near the greater curvature. These mucosal defects increased in number in accordance with the duration of NG administration. At the margins of these mucosal defects, cuboidal cells with hyperchromatic nuclei were observed superficially near the neck zones in most cases. Lesions with these cells increased in number in proportion to the length of NG administration. And they were considered to be regenerative atypical cells possibly originated from the neck cells.
Other finding was the grandular atrophy in the pyloric portions and in the upper parts of fundic portions. No intestinal metaplasia was seen.
Preceding the developement of carcinomas, shallow gastric mucosal defects and regenerative atypical cells were observed at the two common sites as in cancers ever reported.
The possibility of occurance of carcinomas from neck cells in the process of regeneration after the repeated mucosal defects were discussed.