Effects of dietary wheat bran on rat colonic structure and mucosal cell growth.

The effects of dietary wheat bran on colonic morphology and mucosal cell growth were examined in male Wistar rats. Two groups of rats were fed defined diets for 2 weeks. The control group was fed a fiber-free diet while the experimental group received the same diet plus a 20% wheat bran supplement. Nutrient intake and body weight gain were similar in the two groups of rats. The bran-fed group developed an increase in proximal (cecum) and distal colonic weights (P less than 0.02 0.02) but mucosal weight was only increased in the distal colon when compared to the control group (P less than 0.005). Histological measurements revealed deeper colonic crypts (P less than 0.001) and mucosal cell hyperplasia in the bran-fed group in addition to an increase in muscle thickness (P less than 0.001). Mucosal cell hyperplasia, as measured by the increases in mucosal protein (P less than 0.01), DNA (P less than 0.01) and RNA (P less than 0.005) was most marked in the distal colon. Proximal colon showed no significant change in mucosal cell mass. Cell RNA content was decreased only in the proximal colonic mucosa (P less than 0.01). These results demonstrate that dietary wheat bran regulates colonic mucosal cell growth according to the anatomical region of the colon, producing distal mucosal hyperplasia and decreasing proximal colonic cell RNA.