Small intestinal tissue structure and proliferation as influenced by adaptation period and indigestible polysaccharides

Abstract

Growing rats were fed one of five experimental diets differing in polysaccharides for adaptation periods of either 9, 19, 33, 47 or 61 days. The polysaccharides were either plain corn starch (control diet) or plain corn starch substituted with 8% of either cellulose, pectin, guar gum or retrograded starch. The influence of polysaccharides on the epithelial structure and cellular proliferation was evaluated at three different sites in the small intestine (SI). Guar gum and pectin increased the crypt height and proliferative activity in the proximal and mid SI, but not in the distal SI. Guar gum and pectin increased the ratio of crypts per villus in the mid and distal SI. The increase in cell proliferation and migration rate was associated with an expansion of the proliferation zone towards the crypt base. An expansion of the proliferation zone towards the crypt mouth was related mainly to the increased crypt height. As the adaptation period was extended, the crypt villus ratio and the villus height increased in the distal and to some extent in the mid SI. These time-related changes in epithelial structure were accompanied by a decline in migration rates. Interaction between diet and adaptation period appeared insignificant. The changes in epithelial structure and cellular proliferation associated with intake of different indigestible polysaccharides seem to be established as soon as 9 days following introduction of the diet. The changes appear to be permanent, rather than transitional, since the changes lasted throughout the 61 days investigated.