The role of platelets and recombinant factor VIIa on thrombin generation, platelet activation and clot formation
| Autor: | François Depasse, Pantelis Arzoglou, Tahar Chakroun, Ismail Elalamy, Meyer Michel Samama, Grigoris T. Gerotziafas |
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| Rok vydání: | 2004 |
| Předmět: |
Blood Platelets
Hirudin Factor VIIa Pharmacology Thromboplastin Tissue factor Thrombin medicine Humans Platelet Platelet activation Blood Coagulation Hemostasis medicine.diagnostic_test biology Chemistry Platelet Count Hematology Factor VII Platelet Activation Thrombocytopenia Thromboelastography Recombinant Proteins Thrombelastography Kinetics Blood Recombinant factor VIIa Immunology biology.protein circulatory and respiratory physiology medicine.drug |
| Zdroj: | Thrombosis and haemostasis. 91(5) |
| ISSN: | 0340-6245 |
| Popis: | SummaryIn the present study we assessed the effect of platelet counts and rFVIIa on thrombin generation, platelet activation and clot formation after tissue factor pathway activation in human plasma aiming to investigate the mechanism by which rFVIIa induces haemostasis in patients with severe thrombocytopenia. Plasma samples with platelet counts from 5 ×109/l to 150 ×109/l were spiked with rFVIIa (1 µg/ml) or buffer. Clotting was initiated in the presence of diluted thromboplastin. Thrombin generation was assessed using the Thrombogram-Thrombinoscope™ assay. The kinetics of platelet activation was assessed using flow cytometry to measure the expression the Pselectin on platelet membrane of washed platelets suspended in defibrinated homologous PPP. Thromboelastography was used to evaluate the effect of platelets and rFVIIa on the kinetics of clot formation and clot’s firmness. In the presence of low platelet counts the endogenous thrombin potential (ETP) and the maximum concentration of generated thrombin (Cmax) were reduced by 60%-70%.The lag-time of thrombin generation and the time required to reach the Cmax (Tmax) were prolonged, the velocity of platelet activation was decreased and thrombus formation was delayed. Recombinant FVIIa accelerated thrombin generation and platelet activation but it did not significantly modify ETP or Cmax. Recombinant FVIIa enhanced platelet activation in a TF and thrombin dependent manner since its effect on the studied parameters was abolished when TF was omitted or when hirudin was added into the experimental system respectively. Recombinant FVIIa normalized the velocity of clot formation but it did not modify clot firmness, which depended mainly on platelets’ count. In conclusion, in experimental conditions simulating severe thrombocytopenia rFVIIa in the presence of low amounts of TF, accelerates thrombin generation, without increasing the maximum amount of generated thrombin, thus leading in enhanced platelet activation and rapid clot formation. |
| Databáze: | OpenAIRE |
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