INTESTINAL MUCIN DISTRIBUTION IN THE GERM-FREE RAT AND IN THE HETEROXENIC RAT HARBORING A HUMAN BACTERIAL-FLORA - EFFECT OF INULIN IN THE DIET

A colorimetric method was used on water-soluble mucin extracted from m ucosal scrapings and contents of the caecum and the colon of five germ -free (GF) rats and five heteroxenic (NE) rats harbouring a human flor a (GF rats associated with a human flora), These rats were fed on a di et 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 sulpha ted mucins respectively, Spectrocolorimetric assays led to a calculate d absorbance value for 1 mg of the initial mucin extract, Each mucin t ype was compared between treatments, The caecal contents of GF rats co ntained more acidic mucin than sulphomucin, which was present in the s ame 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 th at of the contents: very Little acidic mucin was present and neutral a nd sulphomucin proportions were of the same order of magnitude, Inulin increased the amount of neutral mucin in the caecal contents and of s ulphated mucins in the colonic contents and increased the amounts of n eutral and acidic mucins in the caecal mucosa, Mucin distribution in t he HE rats was very different from that in the GF rats: the caecal con tents contained a high proportion of acidic mucins and very Little sul phomucin. The same distribution of mucins was observed in the colonic contents, The caecal mucosa contained less acidic mucin and more sulph omucin than the caecal contents. Inulin decreased acidic mucins and in creased sulphated mucins in the caecal contents and increased neutral and sulphated mucins in the colonic contents, Inulin increased sulphom ucin in the caecal mucosa and decreased acidic mucin in the caecal and colonic mucosas, The very low amount of mucin that was recovered in t he colonic mucosa suggests that, in the presence of the bacterial flor a and associated with inulin in the diet, mucin was extensively releas ed from the mucosa to the colonic lumen, This might be related to the bacterial metabolites produced.