ENHANCEMENT BY AMINOGUANIDINE OF GASTRIC CARCINOGENESIS INDUCED BY N-METHYL-N'-NITRO-N-NITROSOGUANIDINE IN WISTAR RATS

The effects of prolonged administration of aminoguanidine on gastric c arcinogenesis induced by N-methyl-N-nitro-N-nitrosoguanidine (MNNG), t he ornithine decarboxylase activity of the gastric wall, and the label ing index of the gastric mucosa were investigated in inbred Wistar rat s. The rats received 12.5 or 25.0 mg/kg body weight of aminoguanidine s.c. every other day after oral MNNG treatment for 25 weeks. Prolonged administration of aminoguanidine at 25.0 mg/kg body weight, but not a t 12.5 mg/kg body weight, significantly increased the incidence of gas tric cancers in experimental week 52. However, it did not influence th e histologic types of gastric cancers. Aminoguanidine at 25.0 mg/kg bo dy weight also significantly increased the ornithine decarboxylase act ivity of the antral portion of the gastric wall and the labeling index of the antral epithelial cells. These findings indicate that aminogua nidine enhances gastric carcinogenesis and suggest that its effect may be related to increased proliferation of antral epithelial cells.