DEVELOPMENTAL-CHANGES IN DISTRIBUTION OF THE MUCOUS GEL LAYER AND INTESTINAL PERMEABILITY IN RAT SMALL-INTESTINE

Background: From the developmental aspects, the distribution of fluore scein isothiocyanate dextran 70,000 (FITC-dextran) and mucous gel acro ss the lumen of small intestine was observed as an investigation into the role of mucous gel on intestinal permeability. Furthermore, the ef fect of N-acetyl cysteine (NAC), a mucolytic agent, on intestinal perm eability was examined. Methods: In suckling and weaned rats, FITC-dext ran (750 mg/kg body wt) was gavage-fed. After 3 hours, blood samples w ere taken by cardiac puncture to analyze plasma FITC-dextran by fluore scence spectrometry. Samples of small intestine with luminal contents were frozen and sectioned in a cryostat for fluorescence microscopy; t he same sections were placed in a 0.2% celloidin solution to preserve mucous gel and were stained by periodic acid-Schiff reaction for light microscopy. in weaned rats, intestinal permeability was examined with different concentrations of intraluminally instilled NAG. Results: Th e plasma level of FITC-dextran showed a significant increase (p <.01) in suckling rats compared with the weaned rats. Morphologic findings w ere similar in both the jejunum and ileum: The spaces between villi we re not entirely filled with mucus but filled with FITC-dextran in suck ling rats, whereas the spaces were filled with mucus and not filled wi th FITC-dextran in weaned rats. Intestinal permeability in groups with NAC were significantly higher (P <.01) than that in group without NAG . Conclusions: These results suggest that an increase in the mucous ge l layer that coats the epithelial Lining according to the maturation o f the gastrointestinal tract is one of the most important factors for a restriction in intestinal permeability.