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 i n rat colon. Male F344 rats were given AIN-76A diet that contained cal cium at concentrations of 0.5, 1.0, 2.5, 5.0, 10.0 and 15.0 g/kg in ex periment 1 and 0.2, 2.0 and 6.0 g/kg in experiment 2, One week after t he 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 expo sure 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 calci um reduced the yield of ACF relative to 5.0 g/kg calcium. In experimen t 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 c oncentrations 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 cance r. (C) 1998 Elsevier Science Ireland Ltd.