scholarly journals Effect of calcium ion concentration on the ability of fibrinogen and von Willebrand factor to support the ADP-induced aggregation of human platelets

Blood ◽  
1987 ◽  
Vol 70 (3) ◽  
pp. 827-831 ◽  
Author(s):  
EJ Harfenist ◽  
MA Packham ◽  
RL Kinlough-Rathbone ◽  
M Cattaneo ◽  
JF Mustard
Keyword(s):  
Von Willebrand Factor ◽  
Calcium Ion ◽  
Human Platelets ◽  
Ion Concentration ◽  
Albumin Solution ◽  
High Calcium ◽  
Calcium Ion Concentration ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

To investigate the suggestion that von Willebrand factor (vWf) can substitute for fibrinogen in supporting ADP-induced aggregation of human platelets, we studied platelet reactions in two media: (1) a high calcium medium, Tyrode-albumin solution containing calcium ions in the physiological range of 2 mmol/L, and (2) a low calcium medium, modified Tyrode-albumin solution from which calcium salt was omitted (calcium ion concentration approximately 20 mumol/L). In the high calcium medium vWf even at concentrations up to six times as high as physiological, showed little or no potentiation of ADP-induced platelet aggregation, whereas fibrinogen strongly potentiated reversible aggregation without thromboxane formation or release of granule contents. In the low calcium medium, either vWf or fibrinogen supported biphasic aggregation in response to ADP, with thromboxane formation and release of granule contents. Aspirin and the thromboxane receptor blocker BM 13.177 inhibited these secondary responses to von Willebrand factor, indicating that they require thromboxane A2 formation and feedback amplification by thromboxane A2. A monoclonal antibody, 10E5, to the platelet glycoprotein IIb/IIIa complex inhibited both primary and secondary aggregation. Although vWf supports ADP-induced aggregation when the concentration of ionized calcium is in the micromolar range, it does not support ADP-induced aggregation in the presence of a concentration of ionized calcium in the physiological range, indicating that vWf probably cannot substitute for fibrinogen in supporting ADP- induced aggregation in vivo.

scholarly journals Effect of calcium ion concentration on the ability of fibrinogen and von Willebrand factor to support the ADP-induced aggregation of human platelets

Blood ◽  
1987 ◽  
Vol 70 (3) ◽  
pp. 827-831 ◽  
Author(s):  
EJ Harfenist ◽  
MA Packham ◽  
RL Kinlough-Rathbone ◽  
M Cattaneo ◽  
JF Mustard
Keyword(s):  
Von Willebrand Factor ◽  
Calcium Ion ◽  
Human Platelets ◽  
Ion Concentration ◽  
Albumin Solution ◽  
High Calcium ◽  
Calcium Ion Concentration ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

Abstract To investigate the suggestion that von Willebrand factor (vWf) can substitute for fibrinogen in supporting ADP-induced aggregation of human platelets, we studied platelet reactions in two media: (1) a high calcium medium, Tyrode-albumin solution containing calcium ions in the physiological range of 2 mmol/L, and (2) a low calcium medium, modified Tyrode-albumin solution from which calcium salt was omitted (calcium ion concentration approximately 20 mumol/L). In the high calcium medium vWf even at concentrations up to six times as high as physiological, showed little or no potentiation of ADP-induced platelet aggregation, whereas fibrinogen strongly potentiated reversible aggregation without thromboxane formation or release of granule contents. In the low calcium medium, either vWf or fibrinogen supported biphasic aggregation in response to ADP, with thromboxane formation and release of granule contents. Aspirin and the thromboxane receptor blocker BM 13.177 inhibited these secondary responses to von Willebrand factor, indicating that they require thromboxane A2 formation and feedback amplification by thromboxane A2. A monoclonal antibody, 10E5, to the platelet glycoprotein IIb/IIIa complex inhibited both primary and secondary aggregation. Although vWf supports ADP-induced aggregation when the concentration of ionized calcium is in the micromolar range, it does not support ADP-induced aggregation in the presence of a concentration of ionized calcium in the physiological range, indicating that vWf probably cannot substitute for fibrinogen in supporting ADP- induced aggregation in vivo.

Interactions of Purified Rat Factor VIII/von Willebrand Factor with Rat and Human Platelets – Effect of Albumin and Ristocetin

1984 ◽  
Vol 52 (01) ◽  
pp. 057-059 ◽  
Author(s):  
E Dejana ◽  
M Furlan ◽  
B Barbieri ◽  
M B Donati ◽  
E A Beck
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Rat Plasma ◽  
Human Platelets ◽  
High Concentrations ◽  
Low Sensitivity ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor ◽  
Rat Platelets

SummaryRat platelets do not respond to ristocetin in their own plasma nor do they aggregate in the presence of bovine or porcine factor VIII von Willebrand factor (F VIII R:WF) or human F VIII R:WF in presence of ristocetin. However, rat plasma supports ristocetin induced aggregation of washed human platelets. In this study we report on purification of rat F VIII R:WF from cryoprecipitate. Similarly to porcine or bovine material, purified rat F VIII R:WF induced aggregation of human washed fixed platelets. This effect was enhanced by addition of ristocetin and was not modified by addition of albumin. Rat washed platelets were aggregated by ristocetin in the presence of rat or human F VIII R:WF provided that high concentrations of ristocetin are added in a system essentially free of extraneous proteins. Increasing concentrations of albumin dramatically reduced the ability of ristocetin to aggregate rat platelets while human platelet aggregation by human or rat F VIII R:WF was only moderately affected.These studies show that rat F VIII R:WF can interact with rat and human platelets. The lack of response of rat platelets to ristocetin in their own plasma is most likely due to a low sensitivity of rat platelets to this drug and to an inhibitory activity of plasma proteins on this reaction.

On the Mechanism of Plasmin-induced Aggregation of Human Platelets: Implication of Secreted von Willebrand Factor

1998 ◽  
Vol 79 (06) ◽  
pp. 1191-1198 ◽  
Author(s):  
S. Rabhi-Sabile ◽  
C. de Romeuf ◽  
D. Pidard
Keyword(s):  
Von Willebrand Factor ◽  
Shape Change ◽  
Human Platelets ◽  
Lag Phase ◽  
Distribution Analysis ◽  
Platelet Surface ◽  
Adhesive Proteins ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

SummaryPlasmin triggers a strong metabolic activation in human platelets, leading to shape change and granule exocytosis. However, its capacity to induce cell aggregation remains discussed and, when observed, this aggregation is preceded by a remarkable lag phase. We have thus investigated the effect of plasmin on the adhesive proteins which can be secreted by isolated platelets and mediate cell-to-cell interactions, but are also substrates for the enzyme. Immunoblot analysis of fibrinogen (Fg), thrombospondin-1 (TSP-1), fibronectin (Fn) and von Willebrand factor (vWf) was performed on extracts of platelets exposed under stirring to increasing concentrations of plasmin for up to 10 min at 37° C. Under conditions leading to formation of large aggregates, Fg, Fn and TSP-1 are extensively degraded concomitantly with their secretion, and readily lost from the surface of aggregated cells. Part of the monomers in the platelet vWf are cleaved during secretion into two main fragments with M r ≈180,000 and ≈145,000. However, multimer distribution analysis shows only a slight decrease in the very high molecular weight multimers, and most of the fragmented as well as intact vWf remains associated with the platelet surface when aggregation is maximal. That indeed vWf largely supports plasmin-induced aggregation is suggested by the observation that platelets from a patient with type 3 von Willebrand’s disease, who totally lacks vWf, show little aggregation in response to the enzyme. Finally, plasmin-induced aggregation can be totally inhibited by antagonists of the αIIbβ3 integrin. The present study thus indicates a major role for secreted vWf in platelet aggregation induced by plasmin, through its likely interaction with the multifunctional receptor αIIbβ3.Presented in part at the European Platelet Group Meeting, Erfurt, Germany, May 1996

Lack of Stability of Aggregates after Thrombin-Induced Reaggregation of Thrombin-Degranulated Platelets

1992 ◽  
Vol 67 (04) ◽  
pp. 453-457 ◽  
Author(s):  
Raelene L Kinlough-Rathbone ◽  
Marian A Packham ◽  
Dennis W Perry ◽  
J Fraser Mustard ◽  
Marco Cattaneo
Keyword(s):  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Aggregate Stability ◽  
Relative Importance ◽  
Platelet Aggregates ◽  
The Stability ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

SummaryThe stability of platelet aggregates is influenced by the extent of the release of granule contents; if release is extensive and aggregation is prolonged, deaggregation is difficult to achieve. The relative importance of the contributions of released substances to aggregate stability are not known, although stable thrombin-induced aggregates form in platelet-rich plasma from patients with barely detectable plasma or platelet fibrinogen, and ADP stabilizes thrombin-induced aggregates of platelets from patients with delta storage pool deficiency which otherwise deaggregate more readily than normal platelets. We degranulated platelets with thrombin (0.9 U/ml caused greater than 90% loss of delta and alpha granule contents) and recovered them as individual platelets in fresh medium. The degranulated platelets were reaggregated by thrombin (2 U/ml). To prevent continuing effects of thrombin, FPRCH2C1 was added when thrombin-induced aggregation of thrombin-degranulated platelets reached its maximum. EDTA (5 mM) or EGTA (5 mM) added at maximum aggregation did not deaggregate these platelets, indicating that the stability of these aggregates does not depend on Ca2+ in the medium. Whereas with control platelets a combination of PGE1 (10 μM) and chymotrypsin(10 U/ml) was required for deaggregation, with thrombin-degranulated platelets either PGE1 or chymo-trypsin alone caused extensive deaggregation. The rate and extent of deaggregation of thrombin-degranulated platelets by a combination of PGE1 and chymotrypsin was greater than with control platelets.Electron microscope gold immunocytochemistry using antihuman fibrinogen IgG, anti-von Willebrand factor and anti-fibronectin showed a) that fibrinogen in the vacuoles of degranulated platelets was visible at focal points of platelet contact in the aggregates, but that large areas of platelet contact had no fibrinogen detectable between them; and b) in comparison to fibrinogen, little fibronectin or von Willebrand factor (vWf) was detectable in the platelets.Since the linkages between thrombin-degranulated platelets reaggregated by thrombin can be disrupted either by raising cAMP (thus making glycoprotein IIb/IIIa unavailable) or by proteolysis, these linkages are less stable than those formed between normal platelets. It might therefore be expected that platelets that take part in thrombus formation and then recirculate are likely to form less stable thrombi than platelets that have not released their granule contents.

Further Studies on Aggregation of Platelet-Type von Willebrand’s Disease Platelets by Human von Willebrand Factor

1986 ◽  
Vol 55 (03) ◽  
pp. 338-341 ◽  
Author(s):  
H Takahashi ◽  
W Tatewaki ◽  
M Hanano ◽  
R Nagayama ◽  
A Shibata
Keyword(s):  
Von Willebrand Factor ◽  
Ricinus Communis ◽  
Divalent Cations ◽  
Peanut Agglutinin ◽  
Von Willebrand's Disease ◽  
Von Willebrand’S Disease ◽  
Ricinus Communis Agglutinin ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

SummaryPlatelet-type von Willebrand’s disease (vWD) is a bleeding disorder characterized by a heightened interaction between platelets and von Willebrand factor (vWF) as the result of an intrinsic platelet abnormality (probably in GPIb). Platelet aggregability was nearly normal in response to thrombin, wheat germ agglutinin and Ricinus communis agglutinin in this disorder. Unmodified platelets showed no aggregation upon the addition of peanut agglutinin. Partially purified human vWF induced little aggregation of washed patient platelets, but the aggregation was greatly enhanced in the presence of plasma devoid of vWF. Monoclonal antibodies directed against GPIb and GPIIb/IIIa as well as EDTA completely inhibited vWF-induced aggregation. These results indicate that human vWF induces aggregation of platelet-type vWD platelets in the presence of divalent cations and some plasma cofactor(s), and that both GPIb and GPIIb/IIIa are involved in this aggregation.

The Importance of the Carbohydrate Moiety of the Factor VIII/Von Willebrand Factor Protein in Binding to and Causing Agglutination of Human Platelets

1979 ◽  
Author(s):  
H.R. Gralnick ◽  
D.K. Morisato
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Binding Sites ◽  
Human Platelets ◽  
Galactose Oxidase ◽  
Scatchard Analysis ◽  
Human Fibrinogen ◽  
Number Of Binding Sites ◽  
Von Willebrand ◽  
Willebrand Factor

We have investigated the binding of radiolabelled factor VIII/von Willebrand factor (f. VIII/vWf) protein to human platelets (P) in the presence of ristocetin (R). In these atudies we have delineated the importance of the carbohydrate (CHO) moiety(s) in both the binding to the P and in cauaing agglutination of P. Binding of the f.VIII/vWf protein to human P was time and temperature dependent and dependent on the concentration of R. Binding was specific in that it could not be blocked by human fibrinogen but was inhibited by unlabelled f.VIII/vWf protein. In studies utilizing varying amounts of the f.VIII/vWf protein or by varying the number of P in the assay, the number of binding sites for the f. VIII/vWf protein were estimated at 9,500-9,800 per platelet. Scatchard analysis revealed 11,000 binding sites with 3,600 of high affinity and 7,400 of low affinity. Removal of the sialic acid of the f.VIII/vWf protein resulted in no significa nt change in its ability to bind to the P surface or cause agglutination in the presence, IR. Removal of the galactose by 6-galactosijase resulted in a 75% reduction of binding of the f.VIII/vWf protein and a 91% decrease in the agglutination of human P. Similar studies with galactose oxidase showed that oxidation of the penultimate galactose residue s results in a decrease in agglutination comparable to that seen with 6-galactosidase treatment. These studies indicate that the CHO moiety of the f.VIII/vWf protein is important in both binding to the P surface as well as causing agglutination of human P.

scholarly journals Recurrent Arterial Thrombosis Linked to Autoimmune Antibodies Enhancing von Willebrand Factor Binding to Platelets and Inducing FcγRII Receptor-Mediated Platelet Activation

Blood ◽  
1998 ◽  
Vol 91 (8) ◽  
pp. 2810-2817 ◽  
Author(s):  
Marc F. Hoylaerts ◽  
Chantal Thys ◽  
Jef Arnout ◽  
Jos Vermylen
Keyword(s):  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Low Dose ◽  
Antithyroid Drug ◽  
Fetal Loss ◽  
Thyroid Peroxidase ◽  
Spontaneous Aggregation ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

A patient with a history of recurrent late fetal loss associated with multiple placental infarcts and cerebrovascular ischemia at the age of 36, followed a year later by a myocardial infarction, was referred for further investigation. Coronary angiography was normal. Antinuclear factor, lupus anticoagulant, anticardiolipin antibodies, and other thrombophilia parameters were negative, but there was moderate hyperthyroidism with positive thyroid peroxidase antibodies. Platelet numbers and von Willebrand factor (vWF) were normal. Her platelets showed spontaneous aggregation that disappeared with aspirin intake. However, aggregation still was induced by low levels of ristocetin (0.3 to 0.5 mg/mL). The low-dose ristocetin aggregation in patient platelet-rich plasma (PRP) was completely blocked by neutralizing antiglycoprotein Ib (GPIb) and anti-vWF antibodies. The monoclonal anti-FcγRII receptor antibody IV.3 inhibited partly, which suggests that PRP aggregation by low-dose ristocetin was elicited by vWF-immunoglobulin (Ig) complexes. Upon addition to washed human platelets, with vWF (10 μg/mL), purified patient Igs dose-dependently enhanced ristocetin (0.15 mg/mL)-induced aggregation between 0 and 500 μg/mL, an effect that disappeared again above 1 mg/mL. Aggregation was dependent on the vWF concentration and was blocked by IV.3 or neutralizing anti-GPIb or anti-vWF antibodies. The spontaneous aggregation of normal platelets resuspended in patient plasma could be inhibited totally by IV.3 and partially by neutralizing anti-GPIb or anti-vWF antibodies. Perfusion with normal anticoagulated blood, enriched with 10% of control or patient plasma, over surfaces coated with vWF showed increased platelet adhesion and activation in the presence of patient antibodies. Treatment of the patient with the antithyroid drug thiamazol and temporary corticosteroids, aspirin, and ticlopidine did not correct the platelet hypersensitivity to ristocetin. These observations suggest that some autoantibodies to vWF may both enhance vWF binding to platelets and cause platelet activation through binding to the FcγRII receptor, and thereby may be responsible for a new form of antibody-mediated thrombosis.

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