title: Selective binding of heparins to human endothelial cells. Implications for pharmacokinetics.
abstract: Cultured endothelial cells isolated from human umbilical vein bind heparin and heparin fragments. The binding capacity of endothelial cells for 35S-heparin was for 38% composed of high affinity binding sites (Kd = 11 X 10(-8) M) and for 62% of sites with much lower affinity (Kd = 14 X 10(-7) M). The affinity of unlabeled compounds for heparin binding sites was determined by competition with binding of 125I-heparin. I50 found for unlabeled heparin was 16 X 10(-8) M, which is in agreement with the Kd for binding of heparin to high affinity sites. PK 10169, a low molecular weight fragment of heparin, competed only at relatively high concentrations (I50 = 10(-5) M). Competition experiments with subfractions of PK 10169 showed that I50 was inversely correlated with molecular weight. Gelfiltration of 35S-heparin and 35S-PK 10169 before and after binding to endothelial cells demonstrated a selective binding of high molecular weight molecules from polydisperse heparin and PK 10169 preparations. Bound heparin and PK 10169 molecules were detached from the cell-surface by proteolytic treatment and tested for antifactor-Xa and antifactor-IIa activity. Released heparin is slightly more active in antifactor-Xa and antifactor-IIa activity than its parent preparation. Released PK 10169 was 4 fold more active in antifactor-Xa and 8 fold more active in antifactor-IIa assays than heparin.
authors.affiliation: INSERM U 150, Hôpital Lariboisière, Paris, France.
authors.forename: J L
authors.initials: JL
authors.lastname: van Rijn
authors.forename: M
authors.initials: M
authors.lastname: Trillou
authors.forename: J
authors.initials: J
authors.lastname: Mardiguian
authors.forename: G
authors.initials: G
authors.lastname: Tobelem
authors.forename: J
authors.initials: J
authors.lastname: Caen
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000378:metabolism*; D015951:Factor Xa; D006493:Heparin / Q000493:pharmacokinetics* / Q000494:pharmacology; D006495:Heparin, Low-Molecular-Weight / Q000493:pharmacokinetics / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D010446:Peptide Fragments / Q000493:pharmacokinetics / Q000494:pharmacology; D011516:Prothrombin / Q000037:antagonists & inhibitors; D015842:Serine Proteinase Inhibitors
chemical_list: D006495:Heparin, Low-Molecular-Weight; D010446:Peptide Fragments; D015842:Serine Proteinase Inhibitors; D011516:Prothrombin; C025337:Factor IIa; D006493:Heparin; D015951:Factor Xa