The role of factor XI in thrombin generation induced by low concentrations of tissue factor.
نویسندگان
چکیده
Thrombin generation has been studied in the plasma of severely factor XI deficient patients under conditions in which contact activation did not play a role. In platelet-rich as well as platelet-poor plasma, thrombin generation was dependent upon the presence of factor XI at tissue factor concentrations of between 1 and 20 pg/ml i.e. approximately 0.01 to 0.20% of the concentration normally present in the thromboplastin time determination. The requirement for factor XI is low; significant thrombin generation was seen at 1% factor XI; at 10%, thrombin formation was nearly normalised. A suspension of normal platelets in severely factor XI deficient plasma did not increase thrombin generation. This implies that there is no significant factor XI activity carried by normal platelets, although the presence of factor XI and factor XI inhibitors in platelets cannot be ruled out.
منابع مشابه
Factor XI-dependent reciprocal thrombin generation consolidates blood coagulation when tissue factor is not available.
OBJECTIVE Feedback activation of factor XI by thrombin is a likely alternative for tissue factor-dependent propagation of thrombus formation. However, the hypothesis that thrombin can initiate and propagate its formation in a factor XI-dependent and platelet-dependent manner has not been tested in a plasma milieu. METHODS AND RESULTS We investigated thrombin generation in recalcified platelet...
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Recently, an alternative pathway for factor XI activation has been described in which factor XI is activated by thrombin. Patients with a factor XI deficiency bleed mostly from tissues with high local fibrinolytic activity. Therefore, the role of thrombin-mediated factor XI activation in both fibrin formation and fibrinolysis was studied in a plasma system. clotting was induced by the addition ...
متن کاملFeedback activation of factor XI by thrombin in plasma results in additional formation of thrombin that protects fibrin clots from fibrinolysis.
Recently, an alternative pathway for factor XI activation has been described in which factor XI is activated by thrombin. Patients with a factor XI deficiency bleed mostly from tissues with high local fibrinolytic activity. Therefore, the role of thrombin-mediated factor XI activation in both fibrin formation and fibrinolysis was studied in a plasma system. Clotting was induced by the addition ...
متن کاملWhen and where is factor XI activated by thrombin?
To the Editor. bound to the clot is protected and is no longer subject to inhibition by the competitive substrate, fibrinogen, and is able to catalyze the feedback to activate factor XI and enhance the intrinsic cascade. The pathway by which factor XI is initially activated is still unclear, because the autoactivation of factor is completely inhibited by fibrinogen and high molecular weight kin...
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ورودعنوان ژورنال:
- Thrombosis and haemostasis
دوره 85 6 شماره
صفحات -
تاریخ انتشار 2001