title: Thrombin functions during tissue factor-induced blood coagulation.
abstract: Tissue factor-induced blood coagulation was studied in 20 individuals, for varying periods of time during 54 months, in contact pathway-inhibited whole blood at 37 degrees C and evaluated in terms of the activation of various substrates. After quenching over time with inhibitors, the soluble phases were analyzed for thrombin-antithrombin III (TAT) complex formation, prothrombin fragments, platelet activation (osteonectin release), factor Va generation, fibrinopeptide (FP) A and FPB release, and factor XIII activation. TAT complex formation, for 35 experiments, showed an initiation phase (up to 4.6 +/- 0.6 minutes) in which thrombin was generated at an average rate of 0.93 +/- 0.3 nM/min catalyzed by about 1.3 pM prothrombinase yielding approximately 26 nM thrombin. During a subsequent propagation phase, thrombin was generated at a rate of 83.9 +/- 3.8 nM/min by about 120 pM prothrombinase, reaching ultimate levels of 851 +/- 53 nM. Clot time, determined subjectively, occurred at 4.7 +/- 0.2 minutes and correlated with the inception of the propagation phase. The thrombin concentrations associated with the transitions to rapid product formation are 510 +/- 180 pM for platelet activation (1.9 +/- 0.2 minutes), 840 +/- 280 pM for factor XIII activation and factor Va generation (2.2 +/- 0.6 minutes), 1.3 +/- 0.4 nM for FPA release (2.5 +/- 0.7 minutes), 1.7 +/- 0.5 nM for FPB release and prethrombin 2 (2.8 +/- 0.8 minutes), 7.0 +/- 2.2 nM for thrombin B chain (3.6 +/- 0.2 minutes), and 26 +/- 6.2 nM for the propagation phase of TAT formation (4.6 +/- 0.6 minutes). These results illustrate that the initial activation of thrombin substrates occurs during the initiation phase at less than 2 nM thrombin (0.2%). Most thrombin (96%) is formed well after clotting occurs.
authors.affiliation: Department of Biochemistry, University of Vermont, College of Medicine, Burlington, VT 05405, USA.
authors.forename: Kathleen E
authors.initials: KE
authors.lastname: Brummel
authors.forename: Sara G
authors.initials: SG
authors.lastname: Paradis
authors.forename: Saulius
authors.initials: S
authors.lastname: Butenas
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Mann
mesh_terms: D000328:Adult; D001777:Blood Coagulation / Q000187:drug effects*; D001779:Blood Coagulation Factors / Q000378:metabolism; D002384:Catalysis; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D015676:Osteonectin / Q000378:metabolism; D015539:Platelet Activation; D013379:Substrate Specificity; D013917:Thrombin / Q000378:metabolism* / Q000502:physiology*; D013925:Thromboplastin / Q000494:pharmacology*
chemical_list: D001779:Blood Coagulation Factors; D015676:Osteonectin; D013925:Thromboplastin; D013917:Thrombin