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

The effects of ad libitum feeding of calcium-deficient diet on the incidence, number and histological types of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in male Wistar rats. Rats were fed standard pellet diet containing 0.5% (normal-calcium diet) or 0.01% calcium (calcium-deficient diet) after oral treatment with MNNG for 25 weeks. Oral administration of the calcium-deficient diet resulted in a significant increase in the incidence, but not 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 concentration of the antral portion of the gastric wall and in the labeling index of the antral epithelial cells. These findings indicate that the calcium-deficient diet enhanced gastric carcinogenesis and suggest that its effect may be related to increase in norepinephrine in the gastric wall and consequent stimulation of proliferation of antral epithelial cells.