Modulation of mucosal cell proliferation in the intestine of rats fed a wheat bran diet.

The effect of a 20% wheat bran dietary supplement on intestinal mucosal growth and cell proliferation was examined in two sets of male Sprague-Dawley rats fed defined diets for 4 and 9 wk, respectively. Nutrient intake and body weight gain were equivalent in all groups of animals. In the group of rats fed the bran for 4 wk, small intestinal mucosal weight, DNA, and DNA synthesis, as measured by [3H]thymidine incorporation into DNA, did not change. This was in contrast to large intestinal mucosal DNA which increased by 59.1% in the cecum (p less than 0.001), by 28.3% in the proximal colon (p less than 0.001) and by 35.6% in the distal colon (p less than 0.02) when compared with the controls on the fiber-free diet. Measurements of DNA synthesis and cell proliferation, measured autoradiographically in those rats fed bran for 9 wk, provided evidence of decreased exfoliation in the cecum, with a 45.2% decrease in cell migration (p less than 0.05), whereas in the proximal colon cell proliferation was significantly increased with a cell migration rate 114.3% greater than in the controls (p less than 0.005). These results show that the mechanisms by which wheat bran influences large bowel mucosal growth vary according to the anatomical segment of the intestine. The possible implications of these cytokinetic changes on the development of large bowel cancer are discussed.