ENHANCING EFFECTS OF CALCIUM-DEFICIENT DIET ON GASTRIC CARCINOGENESISBY N-METHYL-N'-NITRO-N-NITROSOGUANIDINE IN WISTAR RATS

The effects of ad libitum feeding of calcium-deficient diet on the inc idence, number and histological types of gastric cancers induced by N- methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in male Wi star rats. Rats were fed standard pellet diet containing 0.5% (normal- calcium diet) or 0.01% calcium (calcium-deficient diet) after oral tre atment with MNNG for 25 weeks. Oral administration of the calcium-defi cient diet resulted in a significant increase in the incidence, but no t the number, of gastric cancers in experimental Week 52. However, it did not affect the histological types of cancer. The calcium-deficient diet also caused a significant increase in tissue norepinephrine conc entration of the antral portion of the gastric wall and in the labelin g index of the antral epithelial cells. These findings indicate that t he calcium-deficient diet enhanced gastric carcinogenesis and suggest that its effect may be related to increase in norepinephrine in the ga stric wall and consequent stimulation of proliferation of antral epith elial cells.