scholarly journals Activation of human factor VII during clotting in vitro

Blood ◽  
1985 ◽  
Vol 65 (1) ◽  
pp. 218-226 ◽  
Author(s):  
LV Rao ◽  
SP Bajaj ◽  
SI Rapaport
Keyword(s):  
Tissue Factor ◽  
Glass Tube ◽  
Factor Vii ◽  
Clotting Factor ◽  
Activate Factor ◽  
Factor Xii ◽  
Factor X ◽  
Normal Plasma

Abstract We have studied factor VII activation by measuring the ratio of factor VII clotting to coupled amidolytic activity (VIIc/VIIam) and cleavage of 125I-factor VII. In purified systems, a low concentration of Xa or a higher concentration of IXa rapidly activated 125I-factor VII, yielding a VIIc/VIIam ratio of 25 and similar gel profiles of heavy and light chain peaks of VIIa. On further incubation, VIIa activity diminished and a third 125I-peak appeared. When normal blood containing added 125I- factor VII was clotted in a glass tube, the VIIc/VIIam ratio rose fivefold, and 20% of the 125I-factor VII was cleaved. Clotting normal plasma in an activated partial thromboplastin time (APTT) system yielded a VIIc/VIIam ratio of 25 and over 90% cleavage of 125I-factor VII. Clotting factor XII-deficient plasma preincubated with antibodies to factor X in an APTT system with added XIa yielded a VIIc/VIIam ratio of 19 and about 60% cleavage, which indicates that IXa, at a concentration achievable in plasma, can effectively activate factor VII. Clotting normal plasma with undiluted tissue factor yielded a VIIc/VIIam ratio of 15 to 20 and 60% cleavage of 125I-factor VII, whereas clotting plasma with diluted tissue factor activated factor VII only minimally. We conclude that both Xa and IXa can function as significant activators of factor VII in in vitro clotting mixtures but believe that only small amounts of factor VII may be activated in vivo during hemostasis.

scholarly journals Activation of human factor VII during clotting in vitro

Blood ◽  
1985 ◽  
Vol 65 (1) ◽  
pp. 218-226 ◽  
Author(s):  
LV Rao ◽  
SP Bajaj ◽  
SI Rapaport
Keyword(s):  
Tissue Factor ◽  
Glass Tube ◽  
Factor Vii ◽  
Clotting Factor ◽  
Activate Factor ◽  
Factor Xii ◽  
Factor X ◽  
Normal Plasma

We have studied factor VII activation by measuring the ratio of factor VII clotting to coupled amidolytic activity (VIIc/VIIam) and cleavage of 125I-factor VII. In purified systems, a low concentration of Xa or a higher concentration of IXa rapidly activated 125I-factor VII, yielding a VIIc/VIIam ratio of 25 and similar gel profiles of heavy and light chain peaks of VIIa. On further incubation, VIIa activity diminished and a third 125I-peak appeared. When normal blood containing added 125I- factor VII was clotted in a glass tube, the VIIc/VIIam ratio rose fivefold, and 20% of the 125I-factor VII was cleaved. Clotting normal plasma in an activated partial thromboplastin time (APTT) system yielded a VIIc/VIIam ratio of 25 and over 90% cleavage of 125I-factor VII. Clotting factor XII-deficient plasma preincubated with antibodies to factor X in an APTT system with added XIa yielded a VIIc/VIIam ratio of 19 and about 60% cleavage, which indicates that IXa, at a concentration achievable in plasma, can effectively activate factor VII. Clotting normal plasma with undiluted tissue factor yielded a VIIc/VIIam ratio of 15 to 20 and 60% cleavage of 125I-factor VII, whereas clotting plasma with diluted tissue factor activated factor VII only minimally. We conclude that both Xa and IXa can function as significant activators of factor VII in in vitro clotting mixtures but believe that only small amounts of factor VII may be activated in vivo during hemostasis.

scholarly journals Reduction of salivary tissue factor (thromboplastin) activity by warfarin therapy

Blood ◽  
1979 ◽  
Vol 53 (3) ◽  
pp. 366-374 ◽  
Author(s):  
LR Zacharski ◽  
R Rosenstein
Keyword(s):  
Tissue Factor ◽  
Vitamin K ◽  
Coagulation Factors ◽  
Human Saliva ◽  
Factor Vii ◽  
Clotting Factor ◽  
Activate Factor ◽  
Total Protein Content ◽  
Factor X ◽  
Clotting Factors

Abstract The coagulant of normal human saliva has been identified as tissue factor (thromboplastin, TF) by virtue of its ability to cause rapid coagulation in plasmas deficient in first-stage coagulation factors and to activate factor x in the presence of factor VII and by virtue of the fact that its activity is expressed only in the presence of factor VII and is inhibited by an antibody to TF. The TF is related to cells and cell fragments in saliva. Salivary TF activity has been found to be significantly reduced in patients taking warfarin. The decline in TF activity during induction of warfarin anticoagulation occurs during the warfarin-induced decline in vitamin-K-dependent clotting factor activity, as judged by the prothrombin time. The decrease in TF activity is not related to a reduction in salivary cell count or total protein content or to a direct effect of warfarin on the assay. It is hypothesized that the mechanism by which warfarin inhibits TF activity may be related to the mechanism by which it inhibits expression of the activity of the vitamin-K-dependent clotting factors. Inhibition of the TF activity may be involved in the antithrombotic effect of warfarin.

scholarly journals Factor VIIa-catalyzed activation of factor X independent of tissue factor: its possible significance for control of hemophilic bleeding by infused factor VIIa

Blood ◽  
1990 ◽  
Vol 75 (5) ◽  
pp. 1069-1073 ◽  
Author(s):  
LV Rao ◽  
SI Rapaport
Keyword(s):  
Tissue Factor ◽  
Factor Viia ◽  
Activate Factor ◽  
Factor X ◽  
Extrinsic Pathway ◽  
Hemophilic Patient ◽  
Factor X Activation ◽  
Rate Of Activation

Abstract Infusing factor VIIa (FVIIa) has been reported to control bleeding in hemophilic patients with factor VIII (FVIII) inhibitors. This is difficult to attribute to an enhanced FVIIa/tissue factor (TF) activation of factor X, since in vitro studies suggest that infusion of FVIIa should neither increase substantially the rate of formation of FVIIa/TF complexes during hemostasis (Proc Natl Acad Sci USA 85:6687, 1988) nor bypass the dampening of TF-dependent coagulation by the extrinsic pathway inhibitor (EPI) (Blood 73:359, 1989). Partial thromboplastin times have also been reported to shorten after infusion of FVIIa. The experiments reported herein establish that shortening of partial thromboplastin times after adding FVIIa to hemophilic plasma in vitro stems from an FVIIa-catalyzed activation of factor X independent of possible trace contamination of reagents with TF. Experiments in purified systems confirmed that FVIIa can slowly activate factor X in a reaction mixture containing Ca2+ and phospholipid but no source of TF. The rate of activation was sufficient to account for the shortening of partial thromboplastin times observed. EPI, which turned off continuing FVIIa/TF activation of factor X, was unable to prevent continuing FVIIa/phospholipid activation of factor X. Because circulating plasma contains only a trace, if any, free FVIIa, such a reaction could never occur physiologically. However, infusing FVIIa creates a nonphysiologic circumstance in which a continuing slow FVIIa/phospholipid catalyzed activation of factor X could conceivably proceed in vivo unimpeded by EPI. Such a mechanism of factor X activation might compensate for an impaired factor IXa/FVIIIa/phospholipid activation of factor X during hemostatis, and therefore control bleeding in a hemophilic patient.

scholarly journals Pseudo-factor-XI deficiency: effect of an inhibitor of factor XI adsorption to surface

Blood ◽  
1981 ◽  
Vol 57 (3) ◽  
pp. 437-443
Author(s):  
S Schiffman ◽  
R Margalit ◽  
M Rosove ◽  
D Feinstein
Keyword(s):  
Partial Thromboplastin Time ◽  
Gel Filtration ◽  
Glass Tube ◽  
Factor Xii ◽  
Contact Activation ◽  
Factor Xi ◽  
Factor Xi Deficiency ◽  
Normal Plasma

Recently we have described a normal plasma activity that modulates contact activation by inhibiting adsorption of factor XI to activating surfaces. Here we report the first identified case in which a patient has abnormal clotting tests due to an excess of a similar activity. The patient's plasma had a prolonged partial thromboplastin time and low apparent factor XI assay. His plasma prolonged the partial thromboplastin time of normal plasma and partially neutralized normal factor XI activity in vivo and in vitro. Analysis in dilute plasma revealed normal amounts of factor XI activity and antigen. Factor XI adsorption from plasma to activating surfaces was tested by adding a small amount of 125I-labeled purified factor XI to plasma, exposing the mixture to a glass tube or kaolin, and determining the amount of factor XI adsorbed to the surface. Whereas normal plasma and plasmas deficient in factor XII, factor XI, or Fletcher factor yielded about 4% adsorption to glass, factor XI adsorption from patient's plasma was less than 1%, indicating the presence of an adsorption inhibitor. This inhibitor did not affect factor XI activation or the activity of preformed factor XIa. It was not adsorbed by AI(OH)3 and was present in serum and the macroglobulin peak on gel filtration of the plasma through Sephadex G-200. The patient's history does not allow a definitive conclusion as to whether this inhibitor was associated with abnormal bleeding.

scholarly journals Factor VIIa-catalyzed activation of factor X independent of tissue factor: its possible significance for control of hemophilic bleeding by infused factor VIIa

Blood ◽  
1990 ◽  
Vol 75 (5) ◽  
pp. 1069-1073 ◽  
Author(s):  
LV Rao ◽  
SI Rapaport
Keyword(s):  
Tissue Factor ◽  
Factor Viia ◽  
Activate Factor ◽  
Factor X ◽  
Extrinsic Pathway ◽  
Hemophilic Patient ◽  
Factor X Activation ◽  
Rate Of Activation

Infusing factor VIIa (FVIIa) has been reported to control bleeding in hemophilic patients with factor VIII (FVIII) inhibitors. This is difficult to attribute to an enhanced FVIIa/tissue factor (TF) activation of factor X, since in vitro studies suggest that infusion of FVIIa should neither increase substantially the rate of formation of FVIIa/TF complexes during hemostasis (Proc Natl Acad Sci USA 85:6687, 1988) nor bypass the dampening of TF-dependent coagulation by the extrinsic pathway inhibitor (EPI) (Blood 73:359, 1989). Partial thromboplastin times have also been reported to shorten after infusion of FVIIa. The experiments reported herein establish that shortening of partial thromboplastin times after adding FVIIa to hemophilic plasma in vitro stems from an FVIIa-catalyzed activation of factor X independent of possible trace contamination of reagents with TF. Experiments in purified systems confirmed that FVIIa can slowly activate factor X in a reaction mixture containing Ca2+ and phospholipid but no source of TF. The rate of activation was sufficient to account for the shortening of partial thromboplastin times observed. EPI, which turned off continuing FVIIa/TF activation of factor X, was unable to prevent continuing FVIIa/phospholipid activation of factor X. Because circulating plasma contains only a trace, if any, free FVIIa, such a reaction could never occur physiologically. However, infusing FVIIa creates a nonphysiologic circumstance in which a continuing slow FVIIa/phospholipid catalyzed activation of factor X could conceivably proceed in vivo unimpeded by EPI. Such a mechanism of factor X activation might compensate for an impaired factor IXa/FVIIIa/phospholipid activation of factor X during hemostatis, and therefore control bleeding in a hemophilic patient.

scholarly journals Characterization of the inhibition of tissue factor in serum

Blood ◽  
1987 ◽  
Vol 69 (1) ◽  
pp. 150-155 ◽  
Author(s):  
GJ Jr Broze ◽  
JP Miletich
Keyword(s):  
Tissue Factor ◽  
Factor Viia ◽  
Factor Xa ◽  
Inhibitory Effect ◽  
Factor Vii ◽  
Factor X ◽  
Human Hepatoma Cells ◽  
Proteolytic Activation

Tissue factor (TF) is a lipoprotein cofactor that markedly enhances the proteolytic activation of factors IX and X by factor VIIa. The functional activity of TF is inhibited by serum in a time- and temperature-dependent fashion. The inhibitory effect is also dependent on the presence of calcium ions and can be reversed by calcium chelation (EDTA) and dilution, thus excluding direct proteolytic destruction of TF as the mechanism for inhibition. Using crude TF, serum immunodepleted of factor VII, and serum depleted of the vitamin K- dependent coagulation factors by BaSO4 absorption, it is shown that TF factor inhibition requires the presence of VII(a), X(a), and an additional moiety contained in barium-absorbed serum. When each of the other required components were at saturating concentrations, half- maximal inhibition of TF occurred in reaction mixtures containing 2% (vol/vol) of TF at a factor VII(a) concentration of 4 ng/mL (80 pmol/L), a factor X concentration of 50 ng/mL (850 pmol/L), and a concentration of barium-absorbed serum of 2.5% (vol/vol). Catalytically active factor Xa appeared to be required for the generation of optimal TF inhibition. The results are consistent with the conclusions of Hjort that barium-absorbed serum contains a moiety that inhibits the VIIa- Ca2+-TF complex. The role of factor X(a) in the generation of the inhibitory phenomenon remains to be elucidated. The inhibitor present in serum (plasma) may in part be produced by the liver in vivo since cultured human hepatoma cells (HepG2) secrete this inhibitory activity in vitro.

scholarly journals Reduction of salivary tissue factor (thromboplastin) activity by warfarin therapy

Blood ◽  
1979 ◽  
Vol 53 (3) ◽  
pp. 366-374 ◽  
Author(s):  
LR Zacharski ◽  
R Rosenstein
Keyword(s):  
Tissue Factor ◽  
Vitamin K ◽  
Coagulation Factors ◽  
Human Saliva ◽  
Factor Vii ◽  
Clotting Factor ◽  
Activate Factor ◽  
Total Protein Content ◽  
Factor X ◽  
Clotting Factors

The coagulant of normal human saliva has been identified as tissue factor (thromboplastin, TF) by virtue of its ability to cause rapid coagulation in plasmas deficient in first-stage coagulation factors and to activate factor x in the presence of factor VII and by virtue of the fact that its activity is expressed only in the presence of factor VII and is inhibited by an antibody to TF. The TF is related to cells and cell fragments in saliva. Salivary TF activity has been found to be significantly reduced in patients taking warfarin. The decline in TF activity during induction of warfarin anticoagulation occurs during the warfarin-induced decline in vitamin-K-dependent clotting factor activity, as judged by the prothrombin time. The decrease in TF activity is not related to a reduction in salivary cell count or total protein content or to a direct effect of warfarin on the assay. It is hypothesized that the mechanism by which warfarin inhibits TF activity may be related to the mechanism by which it inhibits expression of the activity of the vitamin-K-dependent clotting factors. Inhibition of the TF activity may be involved in the antithrombotic effect of warfarin.

Activated Peripheral Mononuclear Cells Plus Soluble Plasma Tissue Factor Activate Factors VII and X in Cardiac Surgical Wounds.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 806-806
Author(s):  
Robert W. Colman ◽  
Mohammad M.H. Khan ◽  
Takashi Hattori ◽  
L. Henry Edmunds4
Keyword(s):  
Cardiac Surgery ◽  
Tissue Factor ◽  
Thrombin Generation ◽  
Mononuclear Cells ◽  
Factor Vii ◽  
Activate Factor ◽  
Factor X ◽  
Complex Wound ◽  
Activated Monocytes

Abstract Objectives: This study examines the role of pericardial wound monocytes in thrombin generation during clinical cardiac surgery with cardiopulmonary bypass (CPB). Background: The mechanism by which wound mononuclear cells rapidly express procoagulant activity is unexplained. Methods: Factor VII activation (FVIIa) was measured using recombinant, truncated, soluble tissue factor (rsTF) and various blood cells in vitro. FVIIa was also measured with monocytes and soluble plasma tissue factor taken before CPB and simultaneously from the pericardial wound and perfusion circuit during CPB in thirteen patients. Results: RsTF in combination with monocytes, but not platelets, neutrophils or red cells, accelerates activation of FVII beginning at 1 pmole/L rsTF. Less than 1% rsTF is bound, yet catalytic activity peaks at 7 minutes and decays afterwards. In wound plasma, monocytes are activated (MCP-1 = 29.5 ± 2.1 pmoles/L) and wound plasma tissue factor (wpTF) is substantially elevated (3.64 ± 0.45 pmoles/L) with 81.7% in the supernatant and 18.3% in microparticles. By Western blot all forms of plasma TF migrate at Mr 65 kDa [TF/FVII(FVIIa) complex]. Wound monocytes and C5a activated prebypass or perfusate monocytes plus wpTF convert all available FVII to FVIIa. Activated monocytes plus supernatant TF/FVII(VIIa) more efficiently activate factor X than microparticle TF/FVII(FVIIa). The correlation coefficient (r) between wound thrombin generation (F1.2) and wpTF is 0.944 (p = 0.0004). Conclusions: During clinical cardiac surgery with CPB wound monocytes plus wpTF or microparticle-free, protein fragments of wound tissue factor preferentially accelerate activation of FVII and FX. This system represents a new mechanism of thrombin generation.

Pseudo-factor-XI deficiency: effect of an inhibitor of factor XI adsorption to surface

Blood ◽  
1981 ◽  
Vol 57 (3) ◽  
pp. 437-443 ◽  
Author(s):  
S Schiffman ◽  
R Margalit ◽  
M Rosove ◽  
D Feinstein
Keyword(s):  
Partial Thromboplastin Time ◽  
Gel Filtration ◽  
Glass Tube ◽  
Factor Xii ◽  
Contact Activation ◽  
Factor Xi ◽  
Factor Xi Deficiency ◽  
Normal Plasma

Abstract Recently we have described a normal plasma activity that modulates contact activation by inhibiting adsorption of factor XI to activating surfaces. Here we report the first identified case in which a patient has abnormal clotting tests due to an excess of a similar activity. The patient's plasma had a prolonged partial thromboplastin time and low apparent factor XI assay. His plasma prolonged the partial thromboplastin time of normal plasma and partially neutralized normal factor XI activity in vivo and in vitro. Analysis in dilute plasma revealed normal amounts of factor XI activity and antigen. Factor XI adsorption from plasma to activating surfaces was tested by adding a small amount of 125I-labeled purified factor XI to plasma, exposing the mixture to a glass tube or kaolin, and determining the amount of factor XI adsorbed to the surface. Whereas normal plasma and plasmas deficient in factor XII, factor XI, or Fletcher factor yielded about 4% adsorption to glass, factor XI adsorption from patient's plasma was less than 1%, indicating the presence of an adsorption inhibitor. This inhibitor did not affect factor XI activation or the activity of preformed factor XIa. It was not adsorbed by AI(OH)3 and was present in serum and the macroglobulin peak on gel filtration of the plasma through Sephadex G-200. The patient's history does not allow a definitive conclusion as to whether this inhibitor was associated with abnormal bleeding.

scholarly journals Activation of human factor VII in the initiation of tissue factor- dependent coagulation

Blood ◽  
1986 ◽  
Vol 68 (3) ◽  
pp. 685-691 ◽  
Author(s):  
LV Rao ◽  
SI Rapaport ◽  
SP Bajaj
Keyword(s):  
Tissue Factor ◽  
Factor Ix ◽  
Factor Vii ◽  
Activate Factor ◽  
Factor Xii ◽  
Factor X ◽  
Clotting Time ◽  
Activated Factor Vii ◽  
Peptide Release ◽  
Minimal Generation

Abstract We have used activation peptide release assays to compare factor VII and activated factor VII (VIIa) activation of factor X, normal factor IX (IXN), and a variant factor IX (IXBmLE), which, after activation, is unable to back-activate factor VII. In purified systems, factor VII and VIIa each rapidly activated factor X, but after a one minute lag for factor VII. VIIa also readily activated both IXN and IXBmLE. Factor VII initially failed to activate substantial amounts of either IXN or IXBmLE; on further incubation factor VII activated IXN but not IXBmLE. Activation of IXN began when approximately 10% of factor VII had been converted to VIIa, as measured by 125I-factor VII radioactivity profiles. Adding factor VII to VIIa slowed its activation of IXBmLE. However, in the presence of factor X, factor VII alone rapidly activated IXBmLE. Unlike purified systems, 1 nmol/L VIIa added to factor VII-deficient plasma failed to activate factor IX. Increasing factor VII to 10 nmol/L (plasma concentration) either as native VII or VIIa yielded similar activation curves for factor IX and similar activation curves for factor X. Adding 5% VIIa to factor X-deficient plasma and to factor XII-deficient plasma substantially shortened the dilute tissue factor clotting time of only the former. These data support the hypothesis that factor VII/tissue factor complex initiates tissue factor-dependent clotting through a minimal generation of Xa. This Xa then rapidly back-activates a small amount of factor VII, following which the rates of activation of both factors IX and X increase dramatically.

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