Gastrointestinal adaptation in response to soluble non-available polysaccharides in the rat

Abstract

1. Rats were fed on a control semi-synthetic diet containing insoluble cellulose (Solkafloc; 100 g/kg; control group) as the only source of dietary fibre, or on one of two test diets containing the same quantity of either guar gum or carboxymethylcellulose (CMC). Animals in the test groups showed similar growth rates and food intakes, which were significantly lower than those of the control group. The CMC group produced frequent poorly formed faeces throughout the 21 d feeding period.2. The small intestines of animals in both test groups were significantly longer than those of the control group at the end of the study. The caeca were also enlarged and heavier, particularly in the CMC-fed group.3. The rate of production of mucosal cells was increased in the small and large intestines of both test groups. The CMC-fed group exhibited a particularly high rate in the distal ileum, where the rate of cell divisions per crypt was over three times greater than at the same site in the control group. The increased proliferation was associated with a significant lengthening of the crypts and an approximately 25% increase in the basal width of the villi.4. Mucosal alkaline phosphatase (EC3.1.3.1) and lactase (EC3.2.1.23) levels were lower than those of the control group at proximal and distal sites in the small intestines of both CMC- and guar-gum-fed groups. Altered spatial distributions of maltase (EC3.2.1.20) and sucrase (EC3.2.1.48) activities were also observed in these animals.5. The consumption of at least some gel-forming polysaccharides evidently leads to significant physiological adaptation in the intestinal mucosa of rats, associated with alterations in mucosal cell proliferation. The mechanism underlying this response appears not to be entirely dependent on the physical properties of the chyme.