Receptor-Mediated Clearance of Chondroitin Sulfate Iron Colloid in the Rat Liver

Abstract

Our previous study demonstrated that reticuloendothelial system function can be monitored by in vivo clearance of chondroitin sulfate iron colloid [Ishida, H. et al. (1991): J. Biochem. Biophys. Methods; Ishida, H. et al (1992): J. Biochem. Biophys. Methods; Tsujinaka, T. et al. (1993): JPEN]. In the present study hepatic clearance of radiolabeled chondroitin sulfate iron colloid (CS⁵⁹Fe) was investigated in detail. When administered intravenously, CS⁵⁹Fe was taken up by not only Kupffer cells but also liver endothelial cells and liver parenchymal cells. Radioactivity per 10⁶ cells was highest in Kupffer cells. When binding of CS⁵⁹Fe to isolated liver cells was examined at 4°C, the association of CS⁵⁹Fe showed a good linearity on a double-reciprocal plot, giving N_r (number of receptors) and K_p (membrane-particle constant). N_r was greatest of all for Kupffer cells. When CS⁵⁹Fe was pretreated with plasma, the N_r increased and K_p decreased in Kupffer cells and liver endothelial cells, whereas K_p increased in liver parenchymal cells. However, no influence was found as a result of pre-treatment of CS⁵⁹Fe with fibronectin or heated plasma. The addition of mannan had no effect. This in vitro chondroitin sulfate iron colloid binding assay may be useful to evaluate effects of various mediators on phagocytosis of hepatic cells.