Intestinal mucin distribution in the germ-free rat and in the heteroxenic rat harbouring a human bacterial flora: effect of inulin in the diet

Abstract

A colorimetric method was used on water-soluble much extracted from mucosal scrapings and contents of the caecum and the colon of five germ-free (GF) rats and five heteroxenic (HE) rats harbouring a hnmao flora (GF rats d a t e d with a human flora). These rats were fed on a diet containing either 100 g sucrose/kg or 100 g inulin/kg. Histological stains, periodic acid–Schiff, alcian blue pH 2·5 and alcian blue pH 0·5 were used to discriminate between neutral, acidic and acidic sulphated mucins respectively. Spectrocolorimetric assays led to a calculated absorbance value for 1 mg of the initial much extract. Each much type was compared between treatments. The caecal contents of GF rats contained more acidic mucin than sulphomucin, which was present in the same proportion as neutral mucin. Their colonic contents contained more acidic mucins than sulphomucin, which in turn was more abundant than neutral mucin. Their caecal mucosa mucin distribution differed from that of the contents: very little acidic much was present and neutral and dphomucin proportions were of the same order of magnitude. Inulin increased the amount of neutral much in the caecal contents and of sulphated mucios in the colonic contents and increased the amounts of neutral and acidic mucins in the caecal mucwa. Mucin distribution in the HE rats was very different from that in the GF rats: the caecal contents contained a high proportion of acidic much and very little sulphomucin. The same distribution of mucins was observed in the colonic contents. The caecal mucaw contained less acidic much and more sulphomucin than the caecal contents. Inulin decreased acidic mucins and increased sulphated much in the caecal contents and increased neutral and sulphated mucins in the colonic contents. Inulin increased sulphomucin in the caecal m u m and decreased acidic much in the caecal and colonic mucosas. The very low amount of mucin that was recovered in the colonic mucosa suggests that, in the presence of the bacterial flora and associated with inulin in the diet, much was extensively released from the mucosa to the colonic lumen. This might be related to the bacterial metabolites produced