Promotion by Nialamide of Gastric Carcinogenesis Induced by N‐Methyl‐N′‐nitro‐N‐nitrosoguanidine in Wistar Rats

The effects of nialamide, a monoamine oxidase inhibitor, on the incidence, number, and histology of gastric cancers induced by N‐methyl‐N′‐nitro‐N‐nitrosoguanidine (MNNG) were investigated in male Wistar rats. Rats were given subcutaneously 50 mg/kg body weight of nialamide in depot form every other day after 25 weeks of oral treatment with MNNG. Prolonged alternate‐day administration of nialamide caused a significant increase in the incidence and number of gastric cancers of the glandular stomach in week 52, However, it did not affect the histology of the cancers. Nialamide also caused a significant increase in tissue norepinephrine concentrations in the gastric wall and in the labeling indices of the gastric mucosae. However, nialamide had no influence on serum gastrin levels in the fasting state and after re‐feeding. These findings indicate that nialamide promotes gastric carcinogenesis and that this may be related to its effects in increasing norepinephrine in the gastric wall and stimulating proliferation of gastric epithelial cells.