title: Pharmacologic modulation of thrombin generation associated with human clots by human purified antithrombin alone or in the presence of low molecular weight heparin or unfractionated heparin.
abstract: Procoagulant activities associated with human clots may contribute to thrombus extension. We investigate the inhibition of clot-associated factor Xa and thrombin activities by purified human antithrombin either alone or as combination with a low molecular weight heparin (enoxaparin) as compared with unfractionated heparin (UFH). The standard clots were prepared by recalcification of frozen platelet-poor human plasma. Clot-associated thrombin was measured on the clot after clot incubation in recalcified buffer or recalcified prothrombin solution. The enzymatic reaction was measured using a specific substrate for thrombin (CBS 3447). The thrombin concentration was determined both on the clots and in the reaction mixtures. In parallel, prothrombin fragment 1.2 and thrombin-antithrombin complexes (TAT) were measured using enzyme-linked immunosorbent assay methods. We demonstrated that in the presence of purified human prothrombin and antithrombin (AT), a partial inhibition of clot associated thrombin activity correlated with an increase of TAT complexes. However, antithrombin was unable to inhibit thrombin generation induced by the clot-associated factor Xa. Enoxaparin (low molecular weight heparin) and UFH did not enhance clot-bound thrombin inhibition induced by AT. We conclude that clot-bound thrombin is accessible to human antithrombin alone. AT is also able to inhibit thrombin generated by factor Xa-associated clot. However, neither a low molecular weight heparin or UFH enhanced the effect of AT alone.
authors.affiliation: Laboratoire de Thrombose Expérimentale, Institut des Cordeliers, Université Pierre et Marie Curie, Paris VI, France.
authors.forename: S
authors.initials: S
authors.lastname: Meddahi
authors.forename: L
authors.initials: L
authors.lastname: Bara
authors.forename: H
authors.initials: H
authors.lastname: Fessi
authors.forename: M M
authors.initials: MM
authors.lastname: Samama
mesh_terms: D000990:Antithrombin III / Q000187:drug effects / Q000493:pharmacokinetics; D000991:Antithrombins / Q000494:pharmacology*; D001777:Blood Coagulation / Q000502:physiology; D002118:Calcium / Q000494:pharmacology; D017984:Enoxaparin / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology*; D006495:Heparin, Low-Molecular-Weight / Q000494:pharmacology; D006801:Humans; D010446:Peptide Fragments / Q000187:drug effects / Q000493:pharmacokinetics; D010447:Peptide Hydrolases / Q000187:drug effects / Q000493:pharmacokinetics; D011485:Protein Binding; D011498:Protein Precursors / Q000187:drug effects / Q000493:pharmacokinetics; D011516:Prothrombin / Q000187:drug effects / Q000493:pharmacokinetics / Q000494:pharmacology; D013917:Thrombin / Q000096:biosynthesis* / Q000187:drug effects* / Q000493:pharmacokinetics
chemical_list: D000991:Antithrombins; D017984:Enoxaparin; D006495:Heparin, Low-Molecular-Weight; D010446:Peptide Fragments; D011498:Protein Precursors; C046193:antithrombin III-protease complex; C029733:prothrombin fragment 1; C044183:prothrombin fragment 2; D000990:Antithrombin III; D011516:Prothrombin; D006493:Heparin; D010447:Peptide Hydrolases; D013917:Thrombin; D002118:Calcium