EFFECTS OF GALACTO-OLIGOSACCHARIDE AND BACTERIAL STATUS ON MUCIN DISTRIBUTION IN MUCOSA AND ON LARGE-INTESTINE FERMENTATION IN RATS

The purpose of the present paper was to study the effects of a dietary undigestible carbohydrate and intestinal microflora on mucin distribu tion (neutral, acid, sulphonated), glycolytic activities: beta-D-galac tosidase (EC 3.2.1.23), N-acetyl-beta-D-galactosaminidase (EC 3.2.1.43 ), N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30), alpha-L-fucosidase ( EC 3.2.1.51) and bacterial metabolism (gas production, short-chain fat ty acids (SCFA) and lactic acid caecal concentration) in germ-free (GF ), conventional (CV) and heteroxenic (HE) rats (GF rats associated wit h a human flora). Rats were fed on either a control diet or a diet con taining 40 g trans-galactosylated oligosaccharide (TOS)/kg. In GF rats fed on the control diet caecal pH was almost neutral and glycolytic a ctivities negligible. The number of mucus-containing cells increased f rom the caecum to the colon for the three types of mucin. TOS had no e ffect in the caecum but it modified mucin cell repartition in the colo n. In CV and HE rats fed on the control diet caecal pH was similar (6. 8), but caecal SCFA and lactic acid concentrations (mumol/g) and gas p roduction (ml/24 h) were higher in CV (70, 5.9 and 2-3 respectively) t han in HE rats (32, 4.6 and 0.4 respectively). In CV, as in HE rats, a cid-mucin-containing cells increased from the caecum to the colon and glycolytic activities were similar. TOS reduced acid-mucin-containing cells in the caecum of CV rats by twofold but had no effect in either the caecum or the colon of HE rats. TOS strongly beta-increased galact osidase activity and slightly modified the other glycolytic activities . Its effect on bacterial metabolites depended on bacterial status. Ho wever, comparison between CV and HE rats showed no evident relationshi p between the number of mucus-containing cells and measured bacterial metabolites. Differences between CV and HE rats might be due to bacter ial microflora specificity. TOS had an intrinsic effect on mucus cell distribution in the colon of GF rats. In CV and HE rats the presence o f the flora abolished this effect.