Binding of heparin on the surface of cultured human endothelial cells

³H-labelled heparin was shown to bind to the surface of cultured human endothelial cells. The binding was time dependent, saturable, reversible and trypsin sensitive. The binding capacity corresponds to about 10⁶ molecules of heparin per cell. Labelled material released from the cells retained its ability to bind to antithrombin III. Binding of heparin to endothelial cells as well as its release is suggested to be of importance in the pharmacokinetics of heparin and to influence the non-thrombogenic properties of the endothelial lining during heparin therapy.