Simultaneous assessment of DOACs effect on clot formation and fibrinolysis with the FibWave

SummaryHaemorrhagic metalloproteinases from Bothrops jararaca and other venoms degrade vessel-wall and plasma proteins involved in platelet plug and fibrin clot formation. These enzymes also cause proteolytic digestion of fibrinogen which has been suggested to cause defective platelet function. Fibrinogen degradation by jararhagin, a metalloproteinase from B. jararaca, and the effect of jararhagin fibrinogenolysis on both platelet aggregation and fibrin clot formation were investigated. Jararhagin was found to cleave human fibrinogen in the C-terminal region of the Aα-chain giving rise to a 285-290 kDa fibrinogen molecule lacking the Aα-chain RGD 572-574 platelet-binding site. Platelet binding and aggregation of ADP-activated platelets is unaffected by this modification. This indicates that the lost site is not essential for platelet aggregation, and that the remaining platelet binding sites located in the N-terminal portion of Aα chains (RGD 95-97) and the C-terminal of γ chains (dodecapeptide 400-411) are unaffected by jararhagin-digestion of fibrinogen. Fibrin clot formation with thrombin of this remnant fibrinogen molecule was defective, with poor polymerization of fibrin monomers but normal release of FPA. The abnormal polymerization could be explained by the loss of one of the two complementary polymerization sites required for side-by-side association of fibrin protofibrils. Jararhagin-induced inhibition of platelet function, an important cause of haemorrhage in envenomed patients, is not caused by proteolysis of fibrinogen, as had been thought, and the mechanism remains to be elucidated.

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Fibrin Formation: The Role of the Fibrinogen-Fibrin Monomer Complex

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648007 ◽

1976 ◽

Vol 36 (01) ◽

pp. 037-048 ◽

Cited By ~ 49

Author(s):

Eric P. Brass ◽

Walter B. Forman ◽

Robert V. Edwards ◽

Olgierd Lindan

Keyword(s):

Particle Size ◽

Induction Period ◽

Fibrin Clot ◽

Clot Formation ◽

Appreciable Amount ◽

Buffer System ◽

Homeostatic Mechanism ◽

Fibrin Formation ◽

Fibrin Monomer

SummaryThe process of fibrin formation using highly purified fibrinogen and thrombin was studied using laser fluctuation spectroscopy, a method that rapidly determines particle size in a solution. Two periods in fibrin clot formation were noted: an induction period during which no fibrin polymerization occurred and a period of rapid increase in particle size. Direct measurement of fibrin monomer polymerization and fibrinopeptide release showed no evidence of an induction period. These observations were best explained by a kinetic model for fibrin clot formation incorporating a reversible fibrinogen-fibrin monomer complex. In this model, the complex serves as a buffer system during the earliest phase of fibrin formation. This prevents the accumulation of free polymerizable fibrin monomer until an appreciable amount of fibrinogen has reacted with thrombin, at which point the fibrin monomer level rises rapidly and polymerization proceeds. Clinically, the complex may be a homeostatic mechanism preventing pathological clotting during periods of elevated fibrinogen.

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Platelet Incorporation of Labelled Adenosine and Adenosine Diphosphate

Thrombosis and Haemostasis ◽

10.1055/s-0038-1651356 ◽

1969 ◽

Vol 22 (02) ◽

pp. 304-315 ◽

Cited By ~ 4

Author(s):

E. W Salzman ◽

T. P Ashford ◽

D. A Chambers ◽

Lena L. Neri

Keyword(s):

Platelet Rich Plasma ◽

Adenosine Diphosphate ◽

Platelet Inhibition ◽

Electron Microscopic ◽

Platelet Binding ◽

Minor Degree ◽

A Minor ◽

Plasma Marker ◽

Electron Microscopic Radioautography ◽

Simultaneous Assessment

SummaryAfter incubation of platelet-rich plasma with labelled adenosine or ADP, platelet incorporation of radioactivity was assessed. Platelets were rapidly separated for counting by filtration through cellulose acetate Millipore. Inulin-H3 served as a plasma marker, and triple isotope techniques permitted simultaneous assessment of the behavior of the adenine and phosphate moieties of ADP without washing of platelets. In other experiments, electron microscopic radioautography was employed to trace the label after platelet incorporation.The results were consistent with previous reports that ADP is dephosphorylated in plasma and is incorporated by platelets only as a dephosphorylated residue, probably adenosine. The label crossed the platelet membrane and entered the platelet, where it was distributed in platelet granules and the agranular cell sap. Concentration within granules occurred to a minor degree.The results support the hypothesis that platelet aggregation by ADP occurs without a persistent bond of ADP to the platelet. Inhibition of aggregation by adenosine probably depends on a metabolic or transport process rather than on competition between adenosine and ADP for platelet binding sites.

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Binding of Thrombin to Fibrin

10.1055/s-0038-1665830 ◽

1979 ◽

Author(s):

L. Róka ◽

F. G. Rademacher

Keyword(s):

Antithrombin Iii ◽

Monomer Concentration ◽

Active State ◽

Clot Formation ◽

Constant Amount ◽

Bovine Thrombin

After clot formation using bovine thrombin and bovine fibrinogen, one can detect no longer the total amount of thrombin. The amount missing in the supernatant is trapped in the clot and can be removed in active state after lysing the clot. The capacity for trapping thrombin by a constant amount of fibrin depends on the structure of the fibrinpolymer. This can be shown by producing different kinds of clots by variation of pH or monomer concentration during polymerisation or using Arvinmonomer insted of Thrombinmonomer. The trapped thrombin shows no clotting activity but some activity with chromogenic substrats remains. to neutralize trapped thrombin about 5 times more antithrombin III is necessary than for the same amount of free thrombin. The trapped thrombin diffuses out of the clot indicating the reversibility of the binding of thrombin to fribin.

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