Localization of endotoxin in the rat intestinal epithelium

High levels of circulating lipopolysaccharide (LPS) cause intestinal inflam mation and increased permeability to bacteria and toxins. To better underst and the effects of LPS on the gut, confocal microscopy and immunofluorescen ce staining were used to examine the distribution of LPS in the rat intesti ne after intravenous or enteral administration. LPS was localized in macrop hages in the lamina propria from 1 h to >28 days after intravenous injectio n. LPS was also detected in the epithelial cells from 8 h to 7 days after i njection. In contrast, LPS administered enterally was found in the gut lume n in close proximity to the mucosa but was not detected in enterocytes at a ny time. The concentration of LPS in enterocytes near the villus tip provid es a mechanism for the clearance of endotoxin, by the turnover and shedding of LPS-containing enterocytes into the gut lumen, that has not been previo usly described.