Localization of endotoxin in the rat intestinal epithelium.

High levels of circulating lipopolysaccharide (LPS) cause intestinal inflammation and increased permeability to bacteria and toxins. To better understand the effects of LPS on the gut, confocal microscopy and immunofluorescence staining were used to examine the distribution of LPS in the rat intestine after intravenous or enteral administration. LPS was localized in macrophages in the lamina propria from 1 h to >28 days after intravenous injection. LPS was also detected in the epithelial cells from 8 h to 7 days after injection. In contrast, LPS administered enterally was found in the gut lumen in close proximity to the mucosa but was not detected in enterocytes at any time. The concentration of LPS in enterocytes near the villus tip provides a mechanism for the clearance of endotoxin, by the turnover and shedding of LPS-containing enterocytes into the gut lumen, that has not been previously described.