REVERSIBLE CECAL AND COLONIC ENLARGEMENT INDUCED BY DIETARY FIBER IN RATS

The reversibility of cecal and colonic enlargement induced by dietary fiber ingestion was studied using weanling rats which were raised on a diet containing cellulose or glucomannan (20%) for 4 weeks, then switched to a control diet (fiber-free) and further raised on a control diet for 4 weeks. Both dietary fibers occurred the increase of weight of whole tissue and mucosa and total DNA of cecal and colonic mucosa. But, they did not induce to increase protein/DNA ratio of cecum and colon. The effect of cellulose was greater in the colon than in the cecum, while that of glucomannan was greater in the cecum than in the colon. (Na+K) ATPase activity of cecal and colonic mucosa was significantly higher in the enlarged tissues induced by both dietary fibers. The enlarged tissues returned spontaneously to the level of the control group within a week after a test diet was switched to the control diet. Total DNA and ratios of RNA/DNA and protein/DNA converged until there were no significant differences among the three groups. The stimulated activity of (Na+K) ATPase, also was readily returned in parallel with the reduction of tissue weight after the elimination of dietary fiber from the diet. These results suggest that the physiological and morphological changes induced by dietary fiber in the large intestine are reversible and might be one of adaptations to response to the variable environments in gastrointestinal tract.