Publication Date:
2011-11-18
Description:
Abstract 2251 Thromboelastography (TEG) was used in ∼200 studies published in 2009, is mainly used for global blood coagulation assessment, and is thrombin and fibrinogen concentration-dependent. Reflecting the time course of fibrin polymerization, TEG measures lag time, rate, and maximum amplitude (MA) of clot stiffness, and is substantially enhanced by platelets. To identify more specific fibrin(ogen) determinants potentially relevant to interpretation we investigated MA under different TEG conditions. The procedure utilizes a polymethylmethacrylate (hydrophobic surface) cup and pin set, the cup oscillating through 4° 45' (6 cycles/minute). The pin (sensor) is suspended via a torsion wire, and transmits a tuning fork-like signal, displayed as a graph, as the clot links pin and cup. Clots cross-linked (by factor XIIIa) were shown insoluble in 6 M urea, and were obtained by adding thrombin to fibrinogen solutions, pH 7.4, containing 8 mM CaCl2 and either 50 nM factor XIII or 30% afibrinogenemic plasma with or without gel-sieved platelets (190,000/μl). Except where otherwise stated, 6 μM fibrinogen was employed. In three sets of experiments without platelets, increasing thrombin (0.001 to 2 U /ml) progressively increased MA. For example, levels of 0.005, 0.1, 0.3, and 0.5 U/ml the yielded respective MAs of 16.7, 49, 62.8, and 65.3 mm. TEG enhancement by platelets reflects mainly their binding of the fibrin(ogen) C-terminal γ dodecapeptide and ensuing clot retraction. Several sets of experiments at different fibrinogen concentrations disclosed that the lower the concentration the more pronounced the platelet enhancement. For example, at of 0.3, 1, 3, and 6 μM fibrinogen (thrombin 0.4 U/ml), the respective control MAs were 0, 2.9, 15.9, 30.4, and 44.9 mm. The presence of platelets increased these to 10.6, 30.4, 44.9, and 64.8 mm, respectively. To test the role of the fibrin(ogen) αC region, two coagulable fibrinogen isolates (termed des-αC) lacking major C-terminal segments of varying length from their αC were prepared as described (Mosesson et al, J Biol Chem 249:4656). They displayed
Print ISSN:
0006-4971
Electronic ISSN:
1528-0020
Topics:
Biology
,
Medicine
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