EFFECT OF DIETARY VITAMIN-D(3) (CHOLECALCIFEROL) ON COLON CARCINOGENESIS INDUCED BY 1,2-DIMETHYLHYDRAZINE IN MALE FISCHER 344 RATS

This study examined the effect of increasing dietary vitamin D on chem ically induced colon carcinogenesis. Male Fischer 344 rats were first injected with 1,2-dimethylhydrazine (200 mg/kg) and then fed one of fi ve dietary levels of vitamin D as cholecalciferol (250, 1,000, 2,000, 4,000, and 10,000 IU/kg diet) for nine months. Dietary vitamin D3 had no effect on weight gain. Plasma 25-hydroxyvitamin D3 levels were simi lar for the 1,000 and 2,000 IU/kg groups but varied in a dose-related manner for the other groups. Vitamin D did not significantly alter the tumor incidence in either the distal or the proximal colon. No signif icant differences in the labeling index were found in either the proxi mal or the distal colon. Within the distal colon, the proliferative zo ne increased in a dose-related manner. Distribution of labeled cells w ithin the crypt compartments was not affected by dietary vitamin D. Bo ne and serum minerals in general were unaffected by dietary vitamin D. This study shows that, at this level of dietary calcium, vitamin D di d not affect 1,2-dimethylhydrazine-induced colon carcinogenesis.