Uptake of Fractionated H-Heparin by Isolated Rat Kupffer Cells.

Purpose and Methods. The uptake of fractionated H-heparin by isolated rat Kupffer cells was examined to determine the uptake mechanism. Results. The association of fractionated H-heparin was concentration-dependent with a dissociation constant of 3.4 nM and a maximum association capacity of 1.3 pmol/10 cells, suggesting the involvement of a specialized mechanism. Although 2,4-dinitrophenol inhibited neither the association nor internalization of fractionated H-heparin, lowering the temperature from 37°C to 4°C reduced the internalization of fractionated H-heparin by 70% without affecting the association. Conclusions. It is suggested that the uptake mechanism may differ from receptor-mediated endocytosis of polypeptides and be mediated by scavenger receptors, because organic anions, and several ligands of scavenger receptors, as well as several heparin analogs, inhibit the binding of fractionated H-heparin to Kupffer cells, while phenylarsine oxide, which is known to inhibit the receptor-mediated or absorptive endocytosis of polypeptides, inhibits neither the association nor internalization of fractionated H-heparin. [ABSTRACT FROM AUTHOR]