title: Inhibition of the early stages of the thrombin generation reaction by various glycosaminoglycans.
abstract: Inhibition of thrombin generation was studied in strongly diluted human plasma by continuously measuring the splitting of the thrombin-specific chromogenic substrate S2288 as a function of the inhibitor concentration. To avoid the activation of clotting cascade proenzymes other than prothrombin, the thrombin generation reaction was initiated by a mixture of calcium, phospholipids and (bovine) factor Xa. Using this assay we have estimated the relative potency of the following glycosaminoglycans: heparin; a fraction of heparin with high affinity for antithrombin III (high affinity heparin); the low molecular weight heparin Fragmin; the low molecular weight heparinoid Org 10172; a fraction of Org 10172 with high affinity for antithrombin III (high affinity Org 10172) and the O-methyl derivative of the pentasaccharide, representing the minimal structure required for binding to antithrombin III. Based on concentrations expressed in amidolytic anti-Xa units, the descending order of potency observed is: Heparin approximately High Affinity Heparin greater than Fragmin greater than Org 10172 greater than High Affinity Org 10172 greater than O-methyl pentasaccharide. The more potent the glycosaminoglycan the stronger the concentration dependence of its inhibitory effect. These findings could be due to the different, additional anti-thrombin activities of these glycosaminoglycans and/or to their different anti-prothrombinase activities. With the pentasaccharide a striking saturation of the inhibition is observed, due to saturation of the antithrombin III.
authors.affiliation: Scientific Development Group, Organon International B.V., Oss, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Visser
authors.forename: D G
authors.initials: DG
authors.lastname: Meuleman
mesh_terms: D000991:Antithrombins / Q000494:pharmacology; D002809:Chondroitin Sulfates; D002863:Chromogenic Compounds; D003871:Dermatan Sulfate; D006025:Glycosaminoglycans / Q000494:pharmacology*; D006493:Heparin / Q000494:pharmacology; D006495:Heparin, Low-Molecular-Weight / Q000494:pharmacology; D006497:Heparan Sulfate; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D009842:Oligopeptides; D009844:Oligosaccharides / Q000494:pharmacology; D013917:Thrombin / Q000096:biosynthesis*
chemical_list: D000991:Antithrombins; D002809:Chondroitin Sulfates; D002863:Chromogenic Compounds; D003871:Dermatan Sulfate; D006025:Glycosaminoglycans; D006493:Heparin; D006495:Heparin, Low-Molecular-Weight; D006497:Heparan Sulfate; D009842:Oligopeptides; D009844:Oligosaccharides; D013917:Thrombin; C041319:isoleucyl-prolyl-arginine-4-nitroanilide; C049714:IC 831423; C035838:danaparoid