Effects of Feeding Regimen on 1,2-Dimethylhydrazine-Induced Intestinal Carcinogenesis in Rats

The effects of feeding regimens on 1,2-dimethylhydrazine (DMH)-induced intestinal carcinogenesis were investigated in male Wistar strain rats. The development of intestinal tumors in rats fed the semipurified powdered diet (SPD) required a longer latent time than that of rats fed the basal pelleted diet (BPD) and the incidence of the tumors, especially adenomas and well differentiated adenocarcinomas, also significantly decreased in the SPD group. However, the incidence of liver cell carcinomas was higher in the SPD group than in the BPD group. Total bile acid levels in bile were not affected by the diet, but bile acid secretion per hour in the SPD group significantly decreased due to the decrease of bile secretion. Moreover, in the SPD group the colonic epithelial cell proliferation was depressed and the cell cycle time was prolonged when compared to that in the BPD group. These changes might result in a significant decreased incidence of adenomas and well differentiated adnocarcinomas in the SPD group.
These results indicate that feeding regimens play an important role in the proliferation of intestinal epithelial cells and the bile secretion and that they influence not only the development of intestinal tumors but also the organospecific carcinogenesis induced by DMH.