SEROSAL BUT NOT MUCOSAL ENDOTOXIN EXPOSURE INCREASES INTESTINAL PERMEABILITY IN-VITRO IN THE RAT

Background: Microbial endotoxins are normally present in the gut, usua lly without apparent harmful effects, whereas systemically administere d endotoxin impairs the mucosal barrier function. Our aim was to inves tigate whether in vitro exposure to bacterial lipopolysaccharide (LPS) could affect the intestinal barrier properties of the rat small intes tine. Methods: Small-intestinal segments from rats were mounted in Uss ing diffusion chambers, and the mucosal to serosal permeation of the m arker molecules bovine serum albumin (BSA) and Cr-51-ethylenediaminete traacetic acid (EDTA) was measured after addition of LPS to the mucosa l or serosal side. Results: Mucosal exposure to LPS (0.01, 0.05, 0.25 mg/ml) had no effects on the permeation of BSA and Cr-51-EDTA, whereas when added to the serosal side at 0.05 or 0.25 mg/ml, LPS increased t he marker permeation. Conclusion: Serosal LPS exposure in vitro increa sed the intestinal permeability to the different-sized markers, wherea s mucosal LPS did not, indicating that the mechanisms leading to intes tinal barrier impairment can be initiated in the intestinal wall itsel f.