EFFECTS OF PERORALLY APPLIED ENDOTOXIN ON COLONIC MUCINS OF GERM-FREERATS

Background: The intestinal epithelium, with the potential to restrict luminal noxae from the host, secretes a mucous layer with various prot ective functions. Microbial colonization of germfree (GF) rats stimula tes this mucin-secreting tissue. The present study determined the effe ct of bacterial lipopolysaccharides (LPS) on this process. Methods: On e, 3, and 5 days after peroral application of 35 mu g LPS/100g body we ight (from Escherichia coli 055:B5), LPS concentrations were monitored in ingesta, intestinal tissue, and liver. Mucin high molecular weight glycoproteins (HMG), released in response to LPS, were isolated and s eparated into mucins, i) attached to the colonic epithelium (EM) and i i mixed to the luminal content (LM), respectively. Subsequently, the b inding capacity of both mucin fractions for various lectins and for ty pe-1 pill expressing E. coli was determined. Results: Ingesta and tiss ue had maximal LPS concentrations on days 3 (jejunum) and 5 (colon). M aximal EM secretion was found on day 3, release of LM further increase d to day 5. Both mucin fractions had altered glycosylation patterns: a ugmentation of beta-galactose, alpha-N-acetyl galactosamine, and manno se coincided with a decrease in alpha-fucose. Compared with the contro ls, attachment of E. coli to EM increased slightly on day 1 only; the binding capacity of LM increased continuously up to day 5. Conclusion: Results suggest that mucins, released in response to LPS, in addition to the epithelial protection, support the gut microbial clearance sys tem.