FACTOR VIII MEDIATES BINDING OF FACTOR IX TO STIMULATED PLATELETS

1987 ◽  
Author(s):  
W Muntean ◽  
B Leschnik
Keyword(s):  
Factor Viii ◽  
Phospholipase C ◽  
Human Platelets ◽  
Final Concentration ◽  
Platelet Lysate ◽  
Factor Ix ◽  
Factor Vii ◽  
Factor X ◽  
Platelet Surface ◽  
Human Thrombin

In previous work we have shown that factor VII! binds to phospholipids of the membrane of stimulated platelets and that von Willebrand factor is not required for binding of factor VIII to platelets. Since factor VIII is a cofactor in the activation of factor X by factor IX, we investigated whether factor VIII enhances binding of factor IX to the platelet surface.Factor VIII and factor IX were purified by immunoadsorbent chromatography using specific rabbit antibodies. Washed human platelets (250/nl final concentration) stimulated by human thrombin and collagen were incubated with barbiturate buffer, or with purified factor IX (1 U/ml final concentration), or with factor IX (1 U/ml) in the presence of factor VIII (1 U/ml). Washed and stimulated platelets were also incubated with factor VIII and IX as above in the presence of different amounts of CaCl2. Platelets were then washed again and lysed by sonication. Factor VIII:Ag (immunoradiometric assay) and factor IX:Ag (ELISA) were measured in the platelet lysate prior to and after incubation of the lysate with phospholipase C.Platelet bound IX:Ag was significantly higher after incubation of stimulated platelets with factor IX in the presence of factor VIII than after incubation of platelets with buffer or with factor IX alone. CaCl2 proved to be essential for binding of factor IX to platelets even in the presence of factor VIII, but CaCl2 was not required for binding of factor VIII to platelets. Measurable VIII :Ag and IX:Ag increased significantly after incubation of the platelet lysate with phospholipase C.Our data suggest that factor VIII mediates binding of factor IX to phospholipids or receptors containing phospholipids on the membrane of stimulated platelets and thereby contributes to the assembly of the factor X activating complex on the platelet surface.

scholarly journals Activation of human factor VII by activated factors IX and X

Blood ◽  
1982 ◽  
Vol 60 (5) ◽  
pp. 1143-1150 ◽  
Author(s):  
DR Masys ◽  
SP Bajaj ◽  
SI Rapaport
Keyword(s):  
Human Factors ◽  
Factor Viii ◽  
Active Site ◽  
Human Factor ◽  
Antithrombin Iii ◽  
Factor Ix ◽  
Factor Vii ◽  
Activate Factor ◽  
Factor X ◽  
Activated Factor Vii

Factor VII clotting activity increases about five-fold when blood is clotted in glass. Prior studies suggested that this results from activation induced by activated factor IX (IXa). However, in purified systems containing phospholipid and calcium, activated factor X (Xa) is known to activate factor VII rapidly. Therefore, we studied activation of factor VII by IXa and X, in systems using purified human factors. Concentrations of IXa and Xa were calculated from total activated protein concentrations rather than from active site concentrations. In the presence of phospolipid and calcium, both IXa and Xa activated factor VII 25-fold; however, Xa was roughly 800 times more efficient than IXa. Without added phospholipid, activation of factor VII by both Xa and IXa was markedly slowed, and Xa was roughly 20 times more efficient than IXa. When both phospholipid and calcium were omitted, activation of factor VII by either enzyme was negligible. Adding normal prothrombin, but not decarboxylated prothrombin, substantially slowed activation of factor VII by both Xa and IXa. Adding thrombin-activated factor VIII and antithrombin-III did not change rates of factor VII activation by either enzyme. These results from purified systems do not provide an explanation for the prior data from plasma systems.

Generation Of Coagulation Factors By The Isolated Rat Liver Perfused With A Synthetic Blood Substitute

1981 ◽  
Author(s):  
C A Owen ◽  
E J W Bowie
Keyword(s):  
Factor Viii ◽  
Rat Liver ◽  
Blood Substitute ◽  
Factor Ix ◽  
Factor Vii ◽  
Clotting Factor ◽  
Isolated Perfused Rat Liver ◽  
Factor Xii ◽  
Factor V ◽  
Factor X

Measuring the release of small amounts of a clotting factor from an isolated perfused rat liver is difficult if the perfusate already contains some of the factor. Further, platelet-containing perfusates generate a coagulant activity that may invalidate clotting assays.We have successfully employed a completely synthetic blood substitute for rat liver perfusions. The perfusate is “Fluosol-43” generously furnished by Alpha Therapeutic Corporation. The oxygen-carrying perfluorochemical is FC-43 (perfluorotributylamine) and the substitute for albumin is hydroxyethyl starch. Using the Brauer perfusion technique, we found that rat livers in 5 hours released an average of 2.3% of the normal plasma concentration of prothrombin, 8.4% factor V, 16.2% factor VII, 7.0% factor IX, 3.7% factor X, 28.3% factor XI and 12.3% factor XII. Antithrombin III and plasminogen were also generated.Only minute amounts of factor VIII were released unless serum, cryoprecipitate or cryoprecipitate-free plasma was added; then the yield was 8.8% on average. The more “venom factor” (platelet aggregability with Bothrops alternata venom) added to the synthetic perfusate, the more factor VIII was released.

Cloning and Characterization of the Murine Coagulation Factor X Gene

2000 ◽  
Vol 83 (05) ◽  
pp. 732-735 ◽  
Author(s):  
Adrian Cooper ◽  
Zhong Liang ◽  
Francis Castellino ◽  
Elliot Rosen
Keyword(s):  
Factor Viii ◽  
Coagulation Factor ◽  
Factor Ix ◽  
Coagulation Factor Viii ◽  
Start Codon ◽  
Factor Vii ◽  
Factor V ◽  
Factor X ◽  
Coagulation Factor Vii ◽  
Coagulation Factor V

SummaryThe gene encoding murine coagulation factor X (fX) was isolated and characterized from a λFIX II library generated from murine genomic DNA. The 20130 bp sequence contains 18049 nucleotides that extend from the initiating methionine to the polyadenylation site. 1056 nucleotides 5’ of the start codon were determined and contain putative start sites for the FX mRNA as well as sites for binding of putative transcription factors. The sequence extends 1024 3’ of the polyadenylattion site.The gene contains 8 exons and 7 introns which were determined by comparing the mouse FX cDNA and gene sequences. The exonic structure of the gene is similar to that of the other mammalian vitamin K-dependent serine proteases of the coagulation system. These include an exon encoding the prepropepetide, the gladomain, a short helical stack, two exons for the two EGF domains, the activation pepetide, and two exons encoding the serine protease domain. The 5’ sequence of the mouse FX gene overlaps with the 3’ region of the FVII gene indicating that the murine FVII and FX gene are arranged in a head to tail arrangement as they are in humans. Abbreviations: fVII, coagulation factor VII; fIX, coagulation factor IX; fX, coagulation factor X; PC, Protein C; fV, coagulation factor V; fVa, activated coagulation factor V; fVIII, coagulation factor VIII; fVIIIa, activated coagulation factor VIII.

scholarly journals Determinants of plasma factor VIIa levels in humans

Blood ◽  
1995 ◽  
Vol 86 (8) ◽  
pp. 3021-3025
Author(s):  
S Eichinger ◽  
PM Mannucci ◽  
F Tradati ◽  
AA Arbini ◽  
RD Rosenberg ◽  
...  
Keyword(s):  
Factor Viii ◽  
Factor Viia ◽  
Factor Ix ◽  
Factor Vii ◽  
Activate Factor ◽  
Functional Assay ◽  
Factor X ◽  
Clotting Factors ◽  
Plasma Factor

Several enzymes can activate factor VII in vitro, but the protease responsible for generating factor VIIa in vivo has not been determined. Using recombinant tissue factor that has undergone a COOH-terminal truncation, a sensitive functional assay has been established for measuring plasma factor VIIa levels. To evaluate the mechanism responsible for the generation of factor VIIa in vivo, we measured the levels of this enzyme after administering purified concentrates of factor IX and factor VIII to patients with severe deficiencies of these clotting factors. In patients with hemophilia B, factor VIIa levels were initially reduced to 0.5 +/- 0.1 ng/mL and gradually increased to normal after infusing 100 U/kg of body weight (BW) of factor IX. Despite these increases, there were no significant changes in the generation of factor Xa or thrombin. In patients with hemophilia A, only a slight reduction in factor VIIa levels (2.5 +/- 1.3 ng/mL) was observed as compared with controls (3.3 +/- 1.1 ng/mL) and no significant changes were observed after factor VIII levels were normalized. The administration of recombinant factor VIIa (10 micrograms/kg BW) to patients with factor VII deficiency increased the mean circulating level of the enzyme to 118 ng/mL, but this only resulted in normalization of the levels of the activation peptides of factor IX and factor X. The above data indicate that factor IXa is primarily responsible for the basal levels of free factor VIIa generated in vivo (ie, in the absence of thrombosis or provocative stimuli) and that changes in the plasma concentrations of free factor VIIa in the blood do not necessarily lead to alterations in the extent of factor X activation.

scholarly journals Recombinant human factor VIIa (rFVIIa) in hemophilia: mode of action and evidence to date

2017 ◽  
Vol 8 (12) ◽  
pp. 345-352 ◽  
Author(s):  
Muriel Giansily-Blaizot ◽  
Jean-François Schved
Keyword(s):  
Tissue Factor ◽  
Factor Viia ◽  
Factor Ix ◽  
Factor Vii ◽  
Factor X ◽  
Independent Manner ◽  
Recombinant Activated Factor Vii ◽  
Platelet Surface ◽  
Activated Factor Vii ◽  
Treatment And Prevention

Recombinant activated factor VII (rFVIIa) is a bypassing agent widely used both in the treatment and prevention of hemorrhagic complications due to hemophilia with inhibitor. In such cases, antihemophilic factors cannot be used. The normal physiology of factor VII/ factor VIIa (FVII/FVIIa) in the hemostatic process requires the presence of tissue factor (TF) that links to FVII leading to a FVIIa-TF complex which activates both factor X and factor IX. The therapeutic use of rFVIIa requires high amount of FVIIa. Some studies demonstrate that FVIIa at high doses still requires tissue factor for function, whereas others suggest that FVIIa activates FX directly on the platelet surface, in a TF-independent manner. In the present article, we discuss the arguments supporting both TF-dependent and TF-independent modes of action. Finally, the coexistence of both TF-dependent and TF-independent mechanisms cannot be excluded.

scholarly journals Activation of human factor VII by activated factors IX and X

Blood ◽  
1982 ◽  
Vol 60 (5) ◽  
pp. 1143-1150 ◽  
Author(s):  
DR Masys ◽  
SP Bajaj ◽  
SI Rapaport
Keyword(s):  
Human Factors ◽  
Factor Viii ◽  
Active Site ◽  
Human Factor ◽  
Antithrombin Iii ◽  
Factor Ix ◽  
Factor Vii ◽  
Activate Factor ◽  
Factor X ◽  
Activated Factor Vii

Abstract Factor VII clotting activity increases about five-fold when blood is clotted in glass. Prior studies suggested that this results from activation induced by activated factor IX (IXa). However, in purified systems containing phospholipid and calcium, activated factor X (Xa) is known to activate factor VII rapidly. Therefore, we studied activation of factor VII by IXa and X, in systems using purified human factors. Concentrations of IXa and Xa were calculated from total activated protein concentrations rather than from active site concentrations. In the presence of phospolipid and calcium, both IXa and Xa activated factor VII 25-fold; however, Xa was roughly 800 times more efficient than IXa. Without added phospholipid, activation of factor VII by both Xa and IXa was markedly slowed, and Xa was roughly 20 times more efficient than IXa. When both phospholipid and calcium were omitted, activation of factor VII by either enzyme was negligible. Adding normal prothrombin, but not decarboxylated prothrombin, substantially slowed activation of factor VII by both Xa and IXa. Adding thrombin-activated factor VIII and antithrombin-III did not change rates of factor VII activation by either enzyme. These results from purified systems do not provide an explanation for the prior data from plasma systems.

scholarly journals Determinants of plasma factor VIIa levels in humans

Blood ◽  
1995 ◽  
Vol 86 (8) ◽  
pp. 3021-3025 ◽  
Author(s):  
S Eichinger ◽  
PM Mannucci ◽  
F Tradati ◽  
AA Arbini ◽  
RD Rosenberg ◽  
...  
Keyword(s):  
Factor Viii ◽  
Factor Viia ◽  
Factor Ix ◽  
Factor Vii ◽  
Activate Factor ◽  
Functional Assay ◽  
Factor X ◽  
Clotting Factors ◽  
Plasma Factor

Abstract Several enzymes can activate factor VII in vitro, but the protease responsible for generating factor VIIa in vivo has not been determined. Using recombinant tissue factor that has undergone a COOH-terminal truncation, a sensitive functional assay has been established for measuring plasma factor VIIa levels. To evaluate the mechanism responsible for the generation of factor VIIa in vivo, we measured the levels of this enzyme after administering purified concentrates of factor IX and factor VIII to patients with severe deficiencies of these clotting factors. In patients with hemophilia B, factor VIIa levels were initially reduced to 0.5 +/- 0.1 ng/mL and gradually increased to normal after infusing 100 U/kg of body weight (BW) of factor IX. Despite these increases, there were no significant changes in the generation of factor Xa or thrombin. In patients with hemophilia A, only a slight reduction in factor VIIa levels (2.5 +/- 1.3 ng/mL) was observed as compared with controls (3.3 +/- 1.1 ng/mL) and no significant changes were observed after factor VIII levels were normalized. The administration of recombinant factor VIIa (10 micrograms/kg BW) to patients with factor VII deficiency increased the mean circulating level of the enzyme to 118 ng/mL, but this only resulted in normalization of the levels of the activation peptides of factor IX and factor X. The above data indicate that factor IXa is primarily responsible for the basal levels of free factor VIIa generated in vivo (ie, in the absence of thrombosis or provocative stimuli) and that changes in the plasma concentrations of free factor VIIa in the blood do not necessarily lead to alterations in the extent of factor X activation.

Very Low Activated Factor VII and Reduced Factor VII Antigen in Familial Abetalipoproteinaemia

1998 ◽  
Vol 80 (08) ◽  
pp. 233-238 ◽  
Author(s):  
K. A. Mitropoulos ◽  
M. N. Nanjee ◽  
D. J. Howarth ◽  
J. C. Martin ◽  
M. P. Esnouf ◽  
...  
Keyword(s):  
Plasma Concentrations ◽  
Positive Association ◽  
Factor Ix ◽  
Factor Vii ◽  
Unesterified Fatty Acid ◽  
Factor Xii ◽  
Factor X ◽  
Factor Xi ◽  
Activated Factor Vii ◽  
Normal Mean

SummaryAbetalipoproteinaemia is a rare disorder of apolipoprotein B metabolism associated with extremely low plasma concentrations of triglyce-ride. To discover whether the general positive association between factor VII and triglyceride levels extends to this condition, 5 patients were compared with 18 controls. All patients had a triglyceride below 100 μmol/l. Plasma unesterified fatty acid concentration was normal. Although factor IX activity was only slightly reduced (mean 88% standard) and factor IX antigen was normal, mean activated factor VII in patients was strikingly reduced to 34% of that in controls, a level similar to that found in haemophilia B. The patients’ mean factor VII activity and factor VII antigen were also significantly reduced to 54% and 63% of those in controls, respectively. Mean factor XI activity and tissue factor pathway inhibitor activity were reduced in patients to 70% and 75% of control values respectively, while factor XII, factor XI antigen, factor X, prothrombin and protein C were normal.

The Activation of Human Factor X in Sodium Citrate: the Role of Factor VII

1976 ◽  
Vol 36 (01) ◽  
pp. 104-114 ◽  
Author(s):  
D. L Aronson ◽  
A. J Mustafa
Keyword(s):  
Sodium Citrate ◽  
Human Factor ◽  
Deae Cellulose ◽  
Factor Ix ◽  
Factor Vii ◽  
Factor X

SummaryHuman factor X was purified by several different procedures yielding products which had varying amounts of factor VII and factor IX. Treatment with CHC13 during the fractionation of the factor X removed 95% of the factor VII and factor IX activity and the resulting factor X activated more slowly when incubated in 25% sodium citrate. Removal of residual factor VII by DEAE cellulose chromatography yielded a factor X which activated still more slowly and less completely. When the factor VII, removed by chromatography, was added to the chromatographed factor X, the ability to be activated in 25% sodium citrate was restored. Confirmatory evidence for the role of factor VII in this reaction was the inhibition of the conversion of the factor X by both DFP and SBTI.

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