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, hut 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.