The Effect of Collagen Mediated Platelet Release on Plasma Prekallikrein Activation

1984 ◽  
Vol 51 (01) ◽  
pp. 037-041 ◽  
Author(s):  
K M Weerasinghe ◽  
M F Scully ◽  
V V Kakkar
Keyword(s):  
Platelet Aggregation ◽  
Healthy Volunteers ◽  
Platelet Rich Plasma ◽  
Age Groups ◽  
Inhibitory Effect ◽  
Age Group ◽  
Platelet Factor ◽  
Activated Platelets ◽  
Platelet Release ◽  
Collagen Treatment

SummaryCollagen mediated platelet aggregation caused -5.6 ± 6.7% inhibition and +39.1 ± 15.2% potentiation of prekallikrein activation in plasma from normal healthy volunteers between 20–40 and 50–65 years of age, respectively (n = 15, p <0.01). The amouns of platelet factor-four (PF4) released in the two groups were not significantly different. Collagen treatment in the presence of indomethacin caused +11.5 ± 3.6% and +59.6 ± 19.5% potentiation in the 20–40 and 50–65 age groups respectively (p <0.02). Adrenaline mediated platelet aggregation caused -55.2 ± 7.1% and -35.2 ± 8.3% inhibition in the 20–40 and 50–65 age groups, respectively. Collagen treatment of platelet-deficient-plasma and platelet-rich-plasma in EDTA also caused potentiation of prekallikrein activation.The results indicate that the observed degree of prekallikrein activation after platelet aggregation is a net result of the inhibitory effect of PF4 and the potentiatory effect of activated platelets. The potentiatory effect was greater after collagen treatment as compared to adrenaline treatment, and in the 50–65 age group as compared to the 20–40 age group.

Effects of N-(2-Diethylaminoethyl)-N-(2-hydroxy- 2-phenylethyl)-2,5-dichloroaniline (AN 162) on Platelet Function and Blood Coagulation

1971 ◽  
Vol 26 (03) ◽  
pp. 576-587
Author(s):  
R. D Mac Kenzie ◽  
T. R Blohm
Keyword(s):  
Platelet Aggregation ◽  
Blood Clotting ◽  
Platelet Rich Plasma ◽  
Adenosine Diphosphate ◽  
Inhibitory Effect ◽  
Clotting Time ◽  
Clotting Factors ◽  
Platelet Factor ◽  
Inhibition Of Platelet Aggregation

SummaryWhen AN 162 was added to human citrated platelet-rich plasma at 30-300 µg/ml, it inhibited platelet aggregation induced by adenosine diphosphate, collagen, and thrombin. When AN 162 was given orally to guinea pigs at 30 to 100 mg/kg, an in vivo inhibitory effect on platelet aggregability was found. Though it activated platelet factor 3, the concentration of AN 162 required for substantial activation was greater than that for inhibition of platelet aggregation. No effect on plasma clotting factors was found at or below 300 µg/ml. Slight prolongation of whole blood clotting time was found in the rat and monkey.

Functional Characterization of PM6/13, a β3-specific (GPIIIa/CD61) Monoclonal Antibody that Shows Preferential Inhibition of Fibrinogen Binding over Fibronectin Binding to Activated Human Platelets

1998 ◽  
Vol 79 (01) ◽  
pp. 177-185 ◽  
Author(s):  
Ashia Siddiqua ◽  
Michael Wilkinson ◽  
Vijay Kakkar ◽  
Yatin Patel ◽  
Salman Rahman ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Functional Characterization ◽  
Human Platelets ◽  
Western Blots ◽  
Activated Platelets ◽  
Reducing Conditions ◽  
Fibronectin Binding

SummaryWe report the characterization of a monoclonal antibody (MAb) PM6/13 which recognises glycoprotein IIIa (GPIIIa) on platelet membranes and in functional studies inhibits platelet aggregation induced by all agonists examined. In platelet-rich plasma, inhibition of aggregation induced by ADP or low concentrations of collagen was accompanied by inhibition of 5-hydroxytryptamine secretion. EC50 values were 10 and 9 [H9262]g/ml antibody against ADP and collagen induced responses respectively. In washed platelets treated with the cyclooxygenase inhibitor, indomethacin, PM6/13 inhibited platelet aggregation induced by thrombin (0.2 U/ml), collagen (10 [H9262]g/ml) and U46619 (3 [H9262]M) with EC50 = 4, 8 and 4 [H9262]g/ml respectively, without affecting [14C]5-hydroxytryptamine secretion or [3H]arachidonate release in appropriately labelled cells. Studies in Fura 2-labelled platelets revealed that elevation of intracellular calcium by ADP, thrombin or U46619 was unaffected by PM6/13 suggesting that the epitope recognised by the antibody did not influence Ca2+ regulation. In agreement with the results from the platelet aggregation studies, PM6/13 was found to potently inhibit binding of 125I-fibrinogen to ADP activated platelets. Binding of this ligand was also inhibited by two other MAbs tested, namely SZ-21 (also to GPIIIa) and PM6/248 (to the GPIIb-IIIa complex). However when tested against binding of 125I-fibronectin to thrombin stimulated platelets, PM6/13 was ineffective in contrast with SZ-21 and PM6/248, that were both potent inhibitors. This suggested that the epitopes recognised by PM6/13 and SZ-21 on GPIIIa were distinct. Studies employing proteolytic dissection of 125I-labelled GPIIIa by trypsin followed by immunoprecipitation with PM6/13 and analysis by SDS-PAGE, revealed the presence of four fragments at 70, 55, 30 and 28 kDa. PM6/13 did not recognize any protein bands on Western blots performed under reducing conditions. However Western blotting analysis with PM6/13 under non-reducing conditions revealed strong detection of the parent GP IIIa molecule, of trypsin treated samples revealed recognition of an 80 kDa fragment at 1 min, faint recognition of a 60 kDa fragment at 60 min and no recognition of any product at 18 h treatment. Under similar conditions, SZ-21 recognized fragments at 80, 75 and 55 kDa with the 55kDa species persisting even after 18 h trypsin treatment. These studies confirm the epitopes recognised by PM6/13 and SZ-21 to be distinct and that PM6/13 represents a useful tool to differentiate the characteristics of fibrinogen and fibronectin binding to the GPIIb-IIIa complex on activated platelets.

Phospholipase C from Clostridium Perfringens Induces Human Platelet Aggregation in Plasma

1988 ◽  
Vol 59 (02) ◽  
pp. 236-239 ◽  
Author(s):  
Giovanna Barzaghi ◽  
Chiara Cerletti ◽  
Giovanni de Gaetano
Keyword(s):  
Platelet Aggregation ◽  
Receptor Antagonist ◽  
Phospholipase C ◽  
Clostridium Perfringens ◽  
Human Platelet ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Platelet Activating Factor ◽  
Inhibitory Effect ◽  
Thromboxane Receptor Antagonist

SummaryWe studied the aggregating effect of different concentrations of phospholipase C (PLC) (extracted from Clostridium perfringens) on human platelet-rich plasma (PRP). PRP was preincubated with PLC for 3 min at 37° C and the platelet aggregation was followed for 10 min. The threshold aggregating concentration (TAG) of PLC was 3-4 U/ml.We also studied the potentiation of PLC with other stimuli on platelet aggregation. Potentiating stimuli, such as arachidonic acid (AA), ADP. Platelet Activating Factor (PAF) and U-46619 (a stable analogue of cyclic endoperoxides) were all used at subthreshold concentrations. We also studied the possible inhibitory effect of aspirin, apyrase, TMQ, a prostaglandin endoper- oxide/thromboxane receptor antagonist and BN-52021, a PAF receptor antagonist. Only aspirin and apyrase were able to reduce aggregation induced by PLC alone and PLC + AA and PLC + ADP respectively. TMQ and BN-52021 were inactive. In ex vivo experiments oral aspirin (500 mg) partially inhibited platelet aggregation induced by PLC alone, PLC + AA and PLC + ADP 2 and 24 h after administration. Aspirin 20 mg for 7 days also reduced aggregation induced by PLC + AA.

Inhibitory Effect of Staphylokinase on Platelet Aggregation

1993 ◽  
Vol 70 (05) ◽  
pp. 834-837 ◽  
Author(s):  
Akira Suehiro ◽  
Yoshio Oura ◽  
Motoo Ueda ◽  
Eizo Kakishita
Keyword(s):  
Platelet Aggregation ◽  
Human Platelet ◽  
Degradation Products ◽  
Platelet Rich Plasma ◽  
Inhibitory Effect ◽  
Effective Concentration ◽  
Inhibit Platelet Aggregation ◽  
Platelet Suspension ◽  
Washed Platelet ◽  
Human Platelet Aggregation

SummaryWe investigated the effect of staphylokinase (SAK), which has specific thrombolytic properties, on human platelet aggregation. Platelet aggregation induced with collagen was observed following preincubation of platelets in platelet-rich plasma (PRP) or washed platelet suspension (WP) with SAK at 37° C for 30 min. SAK inhibited platelet aggregation in PRP only at the highest examined concentration (1 x 10-4 g/ml). Although SAK did not inhibit platelet aggregation in WP which contained fibrinogen, it did when the platelets had been preincubated with SAK and plasminogen. The most effective concentration in WP was 1 x 10-6 g/ml. The effect could be inhibited by adding aprotinin or α2-antiplasmin. The highest generation of plasmin in the same preincubation fluid was detected at 1 x 10-6 g/ml SAK. We concluded that SAK can inhibit platelet aggregation in WP by generating plasmin and/or fibrinogen degradation products, but is only partially effective in PRP because of the existence of α2-antiplasmin.

The Effect of Barbituric Acid Derivatives on Platelet Function in Vitro and in Vivo

1973 ◽  
Vol 30 (02) ◽  
pp. 315-326
Author(s):  
J. Heinz Joist ◽  
Jean-Pierre Cazenave ◽  
J. Fraser Mustard
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Barbituric Acid ◽  
Platelet Rich Plasma ◽  
Inhibitory Effect ◽  
Primary Response ◽  
Sodium Pentobarbital ◽  
Barbituric Acid Derivatives

SummarySodium pentobarbital (SPB) and three other barbituric acid derivatives were found to inhibit platelet function in vitro. SPB had no effect on the primary response to ADP of platelets in platelet-rich plasma (PRP) or washed platelets but inhibited secondary aggregation induced by ADP in human PRP. The drug inhibited both phases of aggregation induced by epinephrine. SPB suppressed aggregation and the release reaction induced by collagen or low concentrations of thrombin, and platelet adherence to collagen-coated glass tubes. The inhibition by SPB of platelet aggregation was readily reversible and isotopically labeled SPB did not become firmly bound to platelets. No inhibitory effect on platelet aggregation induced by ADP, collagen, or thrombin could be detected in PRP obtained from rabbits after induction of SPB-anesthesia.

Effects of Ticlopidine of Platelet Function in Men with Stable Angina Pectoris

1985 ◽  
Vol 54 (04) ◽  
pp. 808-812 ◽  
Author(s):  
Ulf Berglund ◽  
Henning von Schenck ◽  
Lars Wallentin
Keyword(s):  
Platelet Aggregation ◽  
Angina Pectoris ◽  
Platelet Function ◽  
Plasma Levels ◽  
Platelet Reactivity ◽  
Inhibitory Effect ◽  
Controlled Study ◽  
Double Blind ◽  
Platelet Factor

SummaryThe effects of ticlopidine (T) (500 mg daily) on platelet function were investigated in a double-blind placebo-controlled study in 38 middle-aged men with stable incapacitating angina pectoris. The in vitro platelet reactivity to aggregating agents, the platelet sensitivity to prostacyclin and the plasma levels of platelet specific proteins and fibrinogen were determined before and after 4 and 8 weeks of treatment. T exerted a potent inhibitory effect on ADP- and collagen-induced platelet aggregation. The effect of T was proportional to the pretreatment reactivity to ADP and collagen. The inhibitory effect of T on the epinephrine response was less pronounced. The plasma levels of beta-thromboglobulin, platelet factor 4 and fibrinogen were not influenced by T. The platelet inhibition of prostacyclin was potentiated by T, and it was demonstrated that T and prostacyclin had synergistic inhibitory effects on platelet aggregation.

Functional Involvement of Thrombospondin in Platelet Aggregation Induced by Low Versus High Concentrations of Thrombin

1986 ◽  
Vol 55 (01) ◽  
pp. 136-142 ◽  
Author(s):  
K J Kao ◽  
David M Shaut ◽  
Paul A Klein
Keyword(s):  
Platelet Aggregation ◽  
Binding Sites ◽  
Inhibitory Effect ◽  
Activated Platelets ◽  
Low Concentrations ◽  
Platelet Binding ◽  
Functional Involvement ◽  
Thrombin Activation ◽  
Platelet Aggregates ◽  
High Concentrations

SummaryThrombospondin (TSP) is a major platelet secretory glycoprotein. Earlier studies of various investigators demonstrated that TSP is the endogenous platelet lectin and is responsible for the hemagglutinating activity expressed on formaldehyde-fixed thrombin-treated platelets. The direct effect of highly purified TSP on thrombin-induced platelet aggregation was studied. It was observed that aggregation of gel-filtered platelets induced by low concentrations of thrombin (≤0.05 U/ml) was progressively inhibited by increasing concentrations of exogenous TSP (≥60 μg/ml). However, inhibition of platelet aggregation by TSP was not observed when higher than 0.1 U/ml thrombin was used to activate platelets. To exclude the possibility that TSP inhibits platelet aggregation by affecting thrombin activation of platelets, three different approaches were utilized. First, by using a chromogenic substrate assay it was shown that TSP does not inhibit the proteolytic activity of thrombin. Second, thromboxane B2 synthesis by thrombin-stimulated platelets was not affected by exogenous TSP. Finally, electron microscopy of thrombin-induced platelet aggregates showed that platelets were activated by thrombin regardless of the presence or absence of exogenous TSP. The results indicate that high concentrations of exogenous TSP (≥60 μg/ml) directly interfere with interplatelet recognition among thrombin-activated platelets. This inhibitory effect of TSP can be neutralized by anti-TSP Fab. In addition, anti-TSP Fab directly inhibits platelet aggregation induced by a low (0.02 U/ml) but not by a high (0.1 U/ml) concentration of thrombin. In conclusion, our findings demonstrate that TSP is functionally important for platelet aggregation induced by low (≤0.05 U/ml) but not high (≥0.1 U/ml) concentrations of thrombin. High concentrations of exogenous TSP may univalently saturate all its platelet binding sites consequently interfering with TSP-crosslinking of thrombin-activated platelets.

Platelet Retention in Glass Bead Columns: Further Evidence for the Importance of ADP

Blood ◽  
1974 ◽  
Vol 44 (3) ◽  
pp. 411-425 ◽  
Author(s):  
V. J. McPherson ◽  
M. B. Zucker ◽  
N. M. Friedberg ◽  
P. L. Rifkin
Keyword(s):  
Platelet Aggregation ◽  
Acetylsalicylic Acid ◽  
Glass Bead ◽  
Room Temperature ◽  
Creatine Phosphokinase ◽  
Platelet Rich Plasma ◽  
Creatine Phosphate ◽  
Inhibitory Effect ◽  
Normal Platelet ◽  
Normal Individuals

Abstract Plasma of normal heparinized blood contained 0.284 µM ± SD 0.097 (ADP + ATP) with an ATP:ADP ratio of 2.5:1. Plasma from thrombocytopenic blood contained only 0.106 µM ± 0.073 (ADP + ATP). Blood with normal platelet retention released 0.234 µM ± 0.187 (ADP + ATP) during passage through a glass bead column, with an ATP:ADP ratio of 1.6:1. Significantly less was released in blood with low retention, i.e., samples from patients with von Willebrand’s disease, thrombasthenia, or thrombocytopenia, and some samples from normal individuals. Thus, nucleotides in the plasma of pre- and postcolumn blood appear to be derived from platelets; their release within glass bead columns is closely associated with normal platelet retention. Since release occurred at room temperature and was not prevented by acetylsalicylic acid or accompanied by measurable release of 14C-serotonin, the classic release reaction may not have been responsible. The low retention in platelet-rich plasma was variably increased by adding 0.5 µM ADP, an increase at least partly due to trapping of preformed aggregates. Retention in undisturbed blood was markedly inhibited by creatine phosphokinase with creatine phosphate (CPK-CP) and moderately inhibited by apyrase I (ATPase:ADPase 0.8:1) at an ADP-removing activity between 1 and 5 U/ml, indicating that ADP is essential for retention. At less than 1 U/ml, both apyrase I and II (ATPase: ADPase 2.8:1) enhanced retention in undisturbed blood, but CPK-CP was still inhibitory. These results suggest that enhancement is due to conversion of released ATP to ADP, as shown to occur in studies of platelet aggregation with ATP and ADP. At less than 1 U/ml, all three enzymes protected against the inhibitory effect of disturbance; this protection was marked with apyrase II, moderate with apyrase I and slight with CPK-CP. These observations provide additional evidence that ADP is responsible for the low retention caused by disturbance of the blood.

Effect Of Prostacyclin (PGI2) On Human Platelet Aggregation And Secretion

1981 ◽  
Author(s):  
C M Chesney ◽  
D D Pifer
Keyword(s):  
Platelet Aggregation ◽  
Time Course ◽  
Platelet Rich Plasma ◽  
Dense Granule ◽  
Ionophore A23187 ◽  
Factor V ◽  
Platelet Factor ◽  
Dense Granule Secretion ◽  
Granule Secretion ◽  
Data Representative

PGI2,which increases platelet cAMP(Prostaglandins 13: 389,1977),is a potent inhibitor of aggregation and secretion .We stidued the time course of the same return of platelet function after exposure of platelets to PGI2.Sepharose 2B columns were equilibrated with Tyrode’s albumin buffer, pH7.5 (no Ca2+) containing PGI2 (534nM). Platelet rich plasma was applied and eluted with the same buffer. The filtered platelets(GFP) were then subsampled hourly after elution from the column. Fibrinogen was added to finel concentration of 1.7mg/ml. Platelet aggregation(PA) and release of 14C serotonin (5HT),platelet factor 4(PF4), and factor V (FV) were assayed after stimulation of the platelet by collagen(C), ADP,epinephrine(E), arachidonic acid(AA) and ionophore A23187(I). Data representative of 5 separate studies follow.I(20μg/ml) induced PA was 76%(Ohr),52%(1hr) and 61%(2hr and beyond). Release of 5HT, FV,and PF4 were 60%,1.89u,and 7.97 yg/10 pit, respectively, at time 0 and increased progressively, reaching a plateau at 2 hr. AA(500μg/ml) was 10%(0hr),30%(2hr),68%(3hr) and 8%(4hr). Release of 5HT paralleled PA but release of FV and PF4 remained suppressed for 4 hrs. In contrast α-granule (PF4 and FV)release by C(μg/ml)increased as PA increased while dense granule secretion remained suppressed. PA as well as a and dense granule secretion by ADP (10μM) were minimal during 4 hrs. PA and FV secretion by E (55μM) also remain inhibited for 4 hrs. In spite of this normal dense granule release occurred initially and declined progressively over 4 hours.

Inhibition of Human Platelet Aggregation by the Proteolytic Effect of Streptokinase (SK). Role of the Factor VIII Related Antigen

1975 ◽  
Author(s):  
R. Castillo ◽  
S. Maragall ◽  
J. A. Guisasola ◽  
F. Casals ◽  
C. Ruiz ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Factor Viii ◽  
Platelet Rich Plasma ◽  
Gel Filtration ◽  
Inhibitory Effect ◽  
Factor Viii Related Antigen ◽  
Human Factor Viii ◽  
Induced Aggregation

Defective ADP-induced platelet aggregation has been observed in patients treated with streptokinase. This same effect appears “in vitro” when adding SK to platelet rich plasma (PRP). Classic hemophilia and normal platelet poor plasmas (PPP) treated with SK inhibit the aggregation of washed platelets; plasmin-treated normal human serum also shows an inhibitory effect on platelet aggregation. However, von Willebrand SK-treated plasmas do not inhibit the aggregation of washed platelets. The same results appear when plasmas are previously treated with a rabbit antibody to human factor VIII.This confirms that the antiaggregating effect is mainly linked to the digested factor VIII related antigen.The inhibition of ADP-induced platelet aggregation has been proved in gel filtration-isolated and washed platelets from SK-treated PRP.Defective ristocetin-induced platelet aggregation has also been observed- This action does not appear in washed platelets from SK-treated PRP in presence of normal PPP, but it does in presence of SK-treated PPP, which suggests that the inhibition of the ristocetin-induced aggregation is due to the lack of factor VIII and not to the factor VIII-related products.Heparin, either “in vivo” or “in vitro”, has corrected the antiaggregating effect of SK.

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