Rat intestinal mucosal responses to a microbial flora and different diets.

The effects of diet on the histochemical composition of intestinal mucosubstances and the morphology of the villi and crypts were investigated by comparing the data of germ free and conventionally maintained rats fed either a purified diet or a commercial diet. The influence of intestinal microflora was evaluated by comparing the germ free rats and those harbouring either a conventional rat flora or a human microbial flora. In both germ free rats and those maintained conventionally, feeding a purified diet resulted in shallower crypts in the small intestine but deeper crypts in the large intestine compared with their counterparts fed on the commercial diet. The preliminary data obtained with association of human flora showed a reduction of the villus height and crypt depth in the small intestine and, to some extent, the amount of neutral mucins in the goblet cells of both small and large intestine and an increase in the amount of sulphated mucins in the large intestine. In rats given the commercial diet the periodic acid Schiff staining for neutral mucins was more intense in the upper crypts of the small intestine than in the lower crypts, and to a lesser extent in the upper crypts of the large intestine. These results provide evidence that the dietary composition, microbial flora, as well as the interactions between the dietary constituents and microbial flora change the mucosal architecture and the mucus composition and therefore alter the functional characteristics of the intestinal tract.