DISTRIBUTION AND LOCALIZATION OF MONOPHOSPHORYL LIPID-A IN SELECTED TISSUES OF THE RAT

The distribution and cellular localization of Monophosphoryl Lipid A i n the kidney, liver, lung, spleen, and stomach of rat were investigate d by immunohistochemistry on paraffin embedded tissue sections. Rats w ere sacrificed 24h or 48h following intraperitoneal administration of MPL at a dose of 5mg/Kg. The presence of MPL in selected tissues was i ndicated by a positive reaction to MPL antibody. In the kidneys, MPL w as found in collecting tubules and distal convoluted tubules in the me dulla, whereas the glomerulus was essentially free of it. Regarding li ver, MPL was found to be abundant in hepatocytes but only occasionally present in Kupffer cells. In lungs, both alveolar and bronchiolar mac rophages were positive, indicating the lung can also serve as a possib le site for the elimination of MPL. In spleen, endothelial cells and m acrophages were positive for MPL. In stomach, MPL was detected in the gastric mucosa and vascular endothelial cells. In all the tissues stud ied the intensity of the peroxidase reaction was significantly weaker in 48h samples as compared to corresponding 24h samples indicating pos sible elimination of MPL from these tissues.