Heparin degradation in the endothelial cells.

We analyzed the molecular weight distribution of (125I) heparin fractions bound or internalized by human endothelial cells, using gel permeation chromatography. Our results showed that high molecular weight heparin chains are selectively bound and internalized by endothelial cells. Endocytosis is followed by depolymerization of internalized heparin. Chloroquine prevented depolymerization of internalized heparin, indicating that lysosomal enzymes are involved in this process. Degradation of high molecular weight heparin chains by endothelial cells may contribute to the inactivation of the drug, especially as concerns the antifactor IIa activity.