Fate of 51Cr-labeled lipopolysaccharide in tissue culture cells and livers of normal mice.

Livers of normal mice trapped over 80% of intravenously injected 51Cr-labeled lipopolysaccharide after 1 h. Liver fractionation studies showed that nearly 45% of the labeled endotoxin was associated with cell nuclei, 20% with the mitochondrial-lysosomal fraction, and approximately 30% with the cell sap. Analysis of the distribution of 51Cr-labeled lipopolysaccharide among parenchymal and Kupffer cells showed that over 75% of the in vivo-trapped counts were parenchymal cell associated. Cell populations were approximately 65% parenchymal cells and 35% nonparenchymal cells. Further, six non-reticuloendothelial system tissue culture cell lines were tested for their ability to internalize labeled lipopolysaccharide. In all cells studied, 1 to 4% of the labeled lipopolysaccharide was taken up after 3 h, with greater than 80% of the counts localized in the nuclear fraction. The data show that non-reticuloendothelial system cells can sequester endotoxin both in vivo and in vitro and suggest that parenchymal cells as well as Kupffer cells remove circulating endotoxin from the blood.