Effect of calcium on azoxymethane-induced aberrant crypt foci and cell proliferation in the colon of rats.

Calcium has been proposed for prevention of colon cancer. The effects of calcium on azoxymethane (AOM)-induced aberrant crypt foci (ACP), a putative precancerous lesion, and cell proliferation were determined in rat colon. Male F344 rats were given AIN-76A diet that contained calcium at concentrations of 0.5, 1.0, 2.5, 5.0, 10.0 and 15.0 g/kg in experiment 1 and 0.2, 2.0 and 6.0 g/kg in experiment 2. One week after the rats received these diets, they were given the first of two weekly 15 mg/kg injections of AOM. The rats were killed after 35 days of exposure to the different diets. In experiment 1, exposure to either low (0.5 and 1.0 g/kg) or high (10.0 and 15.0 g/kg) concentrations of calcium reduced the yield of ACF relative to 5.0 g/kg calcium. In experiment 2, exposure to 0.2 and 2.0 g/kg calcium resulted in a lower yield of ACF than 6.0 g/kg. Cell proliferation in ACF and non-involved crypts was reduced in animals that received 0.5 or 15.0 mg/Kg relative to 5.0 mg/kg diet calcium. Our results indicate that both lower and higher concentrations of calcium relative to its standard concentration in AIN-76A diet can prevent ACF and reduce the extent of cell proliferation in the lesion which would likely lead to the prevention of colon cancer.