Effect of plastic bead on gastric carcinogenesis in rats treated with N-methyl-N'-nitro-N-nitrosoguanidine.

Experiments were made on induction of cancer of the glandular stomach of rats by a combination of oral administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and insertion of a plastic bead into the gastric lumen. The incidence of cancer with this combination of treatments was greater than by administration of MNNG alone. Fluoroscopic examination showed that barium sulfate remained in the stomach longer when a bead had been inserted into the gastric lumen. This indicates that after insertion of a bead, MNNG must have remained in the stomach longer, and so the period of exposure of the gastric mucosa to the carcinogen must have increased.