Enhancing effect of cysteamine hydrochloride on the development of gastroduodenal tumors induced by N-methyl-N'-nitro-N-nitrosoguanidine in F344 rats.

The effect of the duodenal ulceration induced by cysteamine hydrochloride on the development of gastroduodenal tumors initiated by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was studied in F344 rats of both sexes. Cysteamine (200 mg/kg body wt.) was administered by gastric intubation at various times, before, during or after a 16 week period of MNNG (100 mg/liter in drinking water) treatment. In the preliminary experiment, while the ulcers induced were confined to the proximal duodenum, the pyloric region of the stomach also showed slight erosion. Five of 25 male rats given cysteamine 2 weeks before the start of MNNG treatment developed adenocarcinoma in the duodenum as compared to 1 case in the MNNG alone group. In addition, animals of both sexes which received cysteamine during MNNG treatment yielded significantly increased incidences of adenocarcinoma in the pyloric area of the stomach. In line with earlier reports, the present findings suggest that mucosal damage and subsequent regeneration or proliferation of mucosa are important co-factors for MNNG-induced gastroduodenal carcinogenesis in rats.