scholarly journals Activation of human platelets by the rabbit anticardiolipin antibodies

Blood ◽  
1992 ◽  
Vol 80 (12) ◽  
pp. 3135-3143 ◽  
Author(s):  
YL Lin ◽  
CT Wang
Keyword(s):  
Solid Phase ◽  
Shape Change ◽  
Human Platelets ◽  
Anticardiolipin Antibodies ◽  
Ion Concentration ◽  
Enzyme Linked Immunosorbent Assay ◽  
Free Calcium ◽  
Dependent Manner ◽  
Platelet Response ◽  
Inhibition Studies

Affinity purified anticardiolipin antibodies (ACLA) raised in rabbits showed cross-reactivities with various negatively charged phospholipids as shown by both the solid phase enzyme-linked immunosorbent assay (ELISA) and inhibition studies. In ELISA, ACLA showed strong cross-reactivity to both sphingomyelin (SM) and phosphatidylethanolamine (PE), but the inhibition studies showed that ACLA failed to bind the aqueous suspensions of SM, PE, and PE/PC (1:1). ACLA bound to resting gel-filtered human platelets (GFP) as shown by both inhibition study and flow cytofluorometric analysis. Western blotting procedure showed that ACLA strongly cross-reacted to an 80-Kd plasma membrane protein. ACLA activated platelet response in a concentration-dependent manner. At less than 10 micrograms/mL, ACLA induced both platelet shape change to spiculate irregular forms as shown by scanning electron microscopy and the phosphorylation of 20-Kd protein. ACLA at more than 10 micrograms/mL caused platelet aggregation and secretion. The aggregation was inhibited by EDTA; aspirin; antimycin A plus 2-deoxyglucose; PGE1; and the F(ab')2 fragment of ACLA. It was not inhibited by monoclonal antibody to Fc receptor (MoAb FcR2). The biochemical events of ACLA-induced platelet response involved the elevation of (1) thromboxane A2 formation, (2) cytosolic free calcium ion concentration ([Ca2+]i), and (3) 47-Kd protein phosphorylation. In addition, the subaggregatory concentration of ACLA showed synergistic platelet activation with that concentration of thrombin, collagen, and epinephrine. The study showed the mechanism involved in ACLA-induced platelet responses.

scholarly journals Activation of human platelets by the rabbit anticardiolipin antibodies

Blood ◽  
1992 ◽  
Vol 80 (12) ◽  
pp. 3135-3143 ◽  
Author(s):  
YL Lin ◽  
CT Wang
Keyword(s):  
Solid Phase ◽  
Shape Change ◽  
Human Platelets ◽  
Anticardiolipin Antibodies ◽  
Ion Concentration ◽  
Enzyme Linked Immunosorbent Assay ◽  
Free Calcium ◽  
Dependent Manner ◽  
Platelet Response ◽  
Inhibition Studies

Abstract Affinity purified anticardiolipin antibodies (ACLA) raised in rabbits showed cross-reactivities with various negatively charged phospholipids as shown by both the solid phase enzyme-linked immunosorbent assay (ELISA) and inhibition studies. In ELISA, ACLA showed strong cross-reactivity to both sphingomyelin (SM) and phosphatidylethanolamine (PE), but the inhibition studies showed that ACLA failed to bind the aqueous suspensions of SM, PE, and PE/PC (1:1). ACLA bound to resting gel-filtered human platelets (GFP) as shown by both inhibition study and flow cytofluorometric analysis. Western blotting procedure showed that ACLA strongly cross-reacted to an 80-Kd plasma membrane protein. ACLA activated platelet response in a concentration-dependent manner. At less than 10 micrograms/mL, ACLA induced both platelet shape change to spiculate irregular forms as shown by scanning electron microscopy and the phosphorylation of 20-Kd protein. ACLA at more than 10 micrograms/mL caused platelet aggregation and secretion. The aggregation was inhibited by EDTA; aspirin; antimycin A plus 2-deoxyglucose; PGE1; and the F(ab')2 fragment of ACLA. It was not inhibited by monoclonal antibody to Fc receptor (MoAb FcR2). The biochemical events of ACLA-induced platelet response involved the elevation of (1) thromboxane A2 formation, (2) cytosolic free calcium ion concentration ([Ca2+]i), and (3) 47-Kd protein phosphorylation. In addition, the subaggregatory concentration of ACLA showed synergistic platelet activation with that concentration of thrombin, collagen, and epinephrine. The study showed the mechanism involved in ACLA-induced platelet responses.

Increased Aggregation and Secretion Responses of Human Platelets when Loaded with the Calcium Fluorescent Probes Quin2 and Fura-2

1987 ◽  
Vol 58 (02) ◽  
pp. 737-743 ◽  
Author(s):  
Frarnçois Lanza ◽  
Alain Beretz ◽  
Martial Kubina ◽  
Jean-Pierre Cazenave
Keyword(s):  
Intracellular Calcium ◽  
Shape Change ◽  
Calcium Ionophore ◽  
Human Platelets ◽  
Arachidonic Acid Metabolism ◽  
Free Calcium ◽  
Membrane Bilayer ◽  
Fluorescent Indicators ◽  
Fura 2 ◽  
Low Concentrations

SummaryIncorporation into human platelets of the calcium fluorescent indicators quin2 or fura-2 at low concentrations used to measure intracellular free calcium leads to the potentiation of the effects of agonists on platelets. This was shown by increased aggregatory and secretory responses of quin2 or fura-2 loaded platelets after stimulation with ADP, PAP and with low concentrations of thrombin, collagen, the endoperoxide analog U-46619 and the calcium ionophore A 23187. Quin2 and fura-2 mediated platelet sensitisation could be due to altered arachidonic acid metabolism since it was inhibited by prior treatment with the cydooxygenase inhibitor acetylsalicylate. In contrast, platelets loaded with higher concentrations of calcium chelators exhibited diminished aggregation responses to all aggregating agents. This latter effect was accompanied by increased fluidity of the platelet plasma membrane bilayer and by the exposure of a new pool of membranes to the outer surface of platelets, as monitored with trimethylammonium- diphenylhexatriene (TMA-DPH) in platelets loaded with the non-fluorescent calcium probe analog MAPT. In contrast, low concentrations of quin2 did not potentiate shape change of platelets activated with ADP. Thus, shape change and aggregation can be influenced separately by intracellular Ca2+ chelators. We conclude that platelet responses are altered by the incorporation of intracellular calcium chelators at concentrations used to monitor intracellular calcium changes.

scholarly journals Anticardiolipin antibodies recognize beta 2-glycoprotein I structure altered by interacting with an oxygen modified solid phase surface.

1994 ◽  
Vol 179 (2) ◽  
pp. 457-462 ◽  
Author(s):  
E Matsuura ◽  
Y Igarashi ◽  
T Yasuda ◽  
D A Triplett ◽  
T Koike
Keyword(s):  
Photoelectron Spectroscopy ◽  
Gamma Ray ◽  
Solid Phase ◽  
Anticardiolipin Antibodies ◽  
Enzyme Linked Immunosorbent Assay ◽  
Polystyrene Surface ◽  
Glycoprotein I ◽  
Latex Beads ◽  
Beta 2 ◽  
Phase Surface

Anticardiolipin antibodies (aCL) derived from the sera of individuals exhibiting the antiphospholipid syndrome (APS) directly bind to beta 2-glycoprotein I (beta 2-GPI), which is adsorbed to an oxidized polystyrene surface. Oxygen atoms were introduced on a polystyrene surface by irradiation with electron or gamma-ray radiation. X-ray photoelectron spectroscopy revealed the irradiated surfaces were oxidized to generate C-O and C = O moieties. aCL derived from either APS patients or (NZW x BXSB)F1 mice bound to beta 2-GPI coated on the irradiated plates, depending on the radiation dose. Antibody binding to beta 2-GPI on the irradiated plates was competitively inhibited by simultaneous addition of cardiolipin (CL)-coated latex beads mixed together with beta 2-GPI but were unaffected by addition of excess beta 2-GPI, CL micelles, or CL-coated latex beads alone. There was a high correlation between binding values of aCL in sera from 40 APS patients obtained by the anti-beta 2-GPI enzyme-linked immunosorbent assay (ELISA) using the irradiated plates and those by the beta 2-GPI-dependent aCL ELISA. Therefore, aCL have specificity for an epitope on beta 2-GPI. This epitope is expressed by a conformational change occurring when beta 2-GPI interacts with an oxygen-substituted solid phase surface.

The Effect of the Intracellular Calcium Chelator Quin-2 on the Platelet Phosphoinositide Metabolism, Protein Phosphorylation and Morphology

1987 ◽  
Vol 58 (03) ◽  
pp. 927-931 ◽  
Author(s):  
D de Chaffoy de Courcelles ◽  
P Roevens ◽  
F Verheyen ◽  
H Van Belle ◽  
F De Clerck
Keyword(s):  
Shape Change ◽  
Human Platelets ◽  
Phosphoinositide Metabolism ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Platelet Morphology ◽  
Receptor Signal ◽  
Microscopic Evaluation ◽  
32P Incorporation ◽  
Phosphatidylinositol 4

SummaryWhen human platelets prelabeled with [32P] orthophosphate were loaded with Quin-2, the 32P-incorporation in phosphatidic acid, phosphatidylinositol-4 phosphate and phosphatidylinositol-4,5 bisphosphate increased, that in phosphatidylinositol decreased. These effects occurred in a Quin-2-concentration- dependent manner. On stimulation of the serotonin-S2 receptor, signal transduction, measured as changes in labeling in phospholipids and phosphoproteins, was altered in the presence of the fluorophore. Microscopic evaluation illustrated that Quin-2 affected platelet morphology as well in resting as in stimulated platelets. A correlation between platelet shape change and myosin light chain phosphorylation was apparent.The data evidence that the Quin-2 that is widely used for fluorometric determination of intracellular Ca2+, affects the metabolism of inositol-containing phospholipids whose breakdown is a key event in Ca2i+-mobilization on excitatory platelet activation. These fluorophore-induced alterations might, besides the Ca2-chelating properties, play an important role in the Ca2+ dependent signalling processes in these cells.

Human Anti-Streptokinase Antibodies Induce Platelet Aggregation in an Fc Receptor (CD32) Dependent Manner

1995 ◽  
Vol 74 (03) ◽  
pp. 938-942 ◽  
Author(s):  
Jamal Lebrazi ◽  
Gérard Helft ◽  
Mustapha Abdelouahed ◽  
Ismaïl Elalamy ◽  
Massoud Mirshahi ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Response Curve ◽  
Human Platelets ◽  
Antibody Concentration ◽  
Dependent Manner ◽  
Platelet Response ◽  
Induce Platelet Aggregation ◽  
Fibrinogen Binding ◽  
Two Factors ◽  
Unimodal Response

SummaryExposure to streptokinase (SK) elicits anti-SK antibodies (Abs), which inhibit fibrinolysis and induce platelet aggregation. The mechanism of the latter is not fully understood, although it seems to involve platelet binding by a plasminogen streptokinase and anti-SK ternary complex. Anti-SK Abs were purified by affinity chromatography from serum of patients having received SK for acute myocardial infarction (AMI), and were shown to be of the IgG type. Their effects were studied with (i) human platelets in citrated plasma in the presence of SK or acetylated plasminogen-SK activator complex (APSAC), and (ii) in washed platelets, resuspended in Tyrode buffer after lowering the ionic strength, in the presence of APSAC (which provides both SK and plasminogen). An antibody concentration-response curve was obtained, showing a plateau in the presence of 0.1 mg/ml IgG. By increasing the concentration of APSAC, we obtained a unimodal response curve, the optimal concentration of APSAC being 0.05 U/ml. Aggregation was suppressed by chelating calcium with EDTA, blocking fibrinogen binding by the synthetic peptide Arg-Gly-Asp-Ser (RGDS), and raising intraplatelet cAMP with Iloprost (a prostacyclin analogue). Aggregation required the interaction of the anti-SK Ab Fc domain with the platelet Fc-gamma receptor type II, also known as CD32, since: (i) it was blocked by the monoclonal antibody IV-3 directed against CD32, (ii) it did not occur with F(ab)’2 fragments, which block the response to the intact IgG. The clinical relevance of these platelet-activating anti-SK antibodies remains to be determined. Two factors might influence clinical outcome: (i) the amount and type of pre-existing anti-SK Abs; (ii) the known interindividual variability of the platelet response to binding and activation by IgG involving the CD32 molecule.

INCREASED AGGREGATION AND SECRETION RESPONSES OF HUMAN PLATELETS WHEN LOADED WITH THE CALCIUM FLUORESCENT PROBES QUIN2 AND FURA-2

1987 ◽  
Author(s):  
F Lanza ◽  
A Beretz ◽  
M Kubina ◽  
J-P Cazenave
Keyword(s):  
Intracellular Calcium ◽  
Shape Change ◽  
Calcium Ionophore ◽  
Human Platelets ◽  
Arachidonic Acid Metabolism ◽  
Free Calcium ◽  
Membrane Bilayer ◽  
Fura 2 ◽  
Low Concentrations ◽  
Platelet Shape

Incubation of human platelets with the fluorescent dye esters quin2-AM (10 μM) or fura-2-AM (1 μM) makes possible the direct measurement of intracellular free calcium ([Ca2+1).Underthese conditions, basal levels of [Ca2+]i of 120 ± 16 nM (n=23) using quin2 and 137 ± 15 nM (n=5) using fura-2 can be measured. Both probes record comparable increases of [Ca2 ]i after stimulation with ADP, thrombin, PAF, or U-46619. Incorporation into human platelets of quin2 or fura-2 at the concentrations used to monitor [Ca2+]i leads to the activation of platelets. This was shown by increased aggregation and secretion responses of quin2or fura-2 loaded platelets after stimulationwith ADP (5 μM), PAF (1 μM) and with low concentrations of thrombin (0.015U/ml), collagen (0.5 μg/ml), the endoperoxide analog U-46619 (0.5 μM) or the calcium ionophore A 23187 (1 μM). Quin2 and fura-2 mediated platelet activation could be due to altered arachidonic acid metabolism, since it was partly inhibited by prior treatment with the cyclooxygenase inhibitor acetylsalicylate (1 μM). In contrast, platelets loaded with higher concentrations of calcium chelators (20 to 100 μM quin2-AM)exhibited diminished aggregation responses to all aggregating agents. Thislatter effectwas accompanied by increased fluidity of theplatelet plasma membrane bilayer and by the exposure of a new pool of membranes at the outer surface of platelets, as monitored withtrimethylammonium-diphenylhexatriene (TMA-DPH) in platelets loaded with thenon-fluorescent calcium probe analog MAPT. Platelet shape change, as measured in the aggregometer, was dose-dependently inhibited after loading of quin2 (10-50 μM quin2-AM), even at concentrations which potentiated aggregation. We conclude that incorporation of intracellular calcium chelators alters platelet responses, including at concentrations used to monitor intracellular calcium changes.

ACTION OF GTPγS [GUANOSINE 5∲-0-(3-THIOPHOSPHATE)] ON SAPONIN-PERMEABILISED PLATELETS: INVOLVEMENT OF 'G' PROTEINS IN PLATELET ACTIVATION

1987 ◽  
Author(s):  
K S Authi ◽  
B J Evenden ◽  
N Crawford
Keyword(s):  
G Protein ◽  
Shape Change ◽  
Second Messengers ◽  
Phosphatidyl Inositol ◽  
Protein S ◽  
Human Platelets ◽  
Dependent Manner ◽  
Guanine Nucleotide Binding Protein ◽  
Intact Cells ◽  
Dose Dependent

Certain ligand-receptor interactions at cell surfaces lead to the phospholipase-C (PLC) hydrolysis of phosphatidyl inositol (4.5) bisphosphate (PIP2). The products serve as intracellular second messengers, e.g. inositol (1.4.5) trisphosphate (IP3) releases Ca2+ from intracellular stores and diacylglycerol activates protein kinase-C. From studies using GTP and analogues (e.g. GTPγS) there is evidence of a key role for a guanine nucleotide binding protein(s) as a link between receptors and PIP2 hydrolysis. We report the actions of GTPγS on washed human platelets permeabilised with saponin (12-14 μg/ml) to allow penetration of low MWt polar substances. The responses to GTPγS are dose dependent (range 9-60 μM) and at 60 μM the agent induces shape change, aggregation and the secretion of 50% of previously incorporated [14C]-5HT. No effect of GTPγS is seen with intact cells. Shape change occurs 25-30 sec after GTPγS; aggregation and secretion is complete after 3 min. When GTP was used (up to 135 μM) with similarly permeabilised platelets no responses were initiated. Phosphatidylinositol turnover was monitored using 32P-labelling before permeabilisation. The addition of 90 μM GTPγS resulted in a 143 ± 23% (n=4) increase in 32P-phosphatidic acid (PA) with respect to the basal levels of “saponised control” cells. These findings suggest that GTPγS stimulates PLC activity through a ‘G’ protein interaction. The GDP analogue (GDPβS) produced no activation responses in saponised platelets but inhibited responses induced by GTPγS in a dose dependent manner (0-480 μM, max inhibition 480 μM). At 960 μM, GDPβS totally inhibited aggregation and secretion initiated by low doses of thrombin (0.1 U/ml) and collagen (1 μg/ml). Identical inhibition by GDPβS of thrombin and collagen-induced activation of intact platelets was observed indicating membrane penetration of this analogue. Shape change effects were not inhibited by GDPSS. The inhibitory effects of GDPSS towards thrombin and collagen induced secretion could be progressively overcome at higher doses of thrombin (0.2 U/ml - 2 U/ml) and collagen (5 μg/ml - 60 μg/ml) suggesting that at higher concentrations these agonists may exert effects through 'G' protein-independent mechanisms.

Some Anticardiolipin Antibodies Recognize a Combination of Phospholipids With Thrombin-Modified Antithrombin, Complement C4b-Binding Protein, and Lipopolysaccharide Binding Protein

Blood ◽  
1999 ◽  
Vol 93 (12) ◽  
pp. 4248-4255 ◽  
Author(s):  
Josiane Arvieux ◽  
Gilles Pernod ◽  
Véronique Regnault ◽  
Luc Darnige ◽  
Jérôme Garin
Keyword(s):  
Bovine Serum ◽  
Binding Protein ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Deae Cellulose ◽  
Anticardiolipin Antibodies ◽  
Enzyme Linked Immunosorbent Assay ◽  
Dependent Manner ◽  
Lipopolysaccharide Binding Protein ◽  
Lipopolysaccharide Binding

Abstract The standard enzyme-linked immunosorbent assay (ELISA) for anticardiolipin antibodies (ACA) detects a heterogenous group of antibodies against cardiolipin on its own, β2-glycoprotein I (β2GPI), and, potentially, other phospholipid-binding plasma proteins from bovine or human origin. In an attempt to identify new proteic targets of ACA, we selected 6 patients who possessed cofactor-dependent ACA but no antibody to human or bovine β2GPI detectable in the β2GPI-ELISA. Three of these samples proved to recognize β2GPI in combination with cardiolipin, but not β2GPI directly immobilized on γ-irradiated polystyrene or agarose beads. In the other cases, the component required for ACA binding was purified from adult bovine serum or plasma by means of ammonium sulfate precipitation and chromatography on Phenyl-Sepharose, diethyl aminoethyl (DEAE)-cellulose, heparin-Ultrogel, and Sephacryl S-300 columns. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis coupled to N-terminal amino acid microsequencing identified the cofactors of patients no. 4, 5, and 6 ACA as lipopolysaccharide binding protein (LBP), complement C4b-binding protein (C4BP), and the thrombin-antithrombin (AT) complex, respectively. Adsorption of each of these cofactor preparations with cardiolipin liposomes led to suppression of ACA reactivity, concomitant with the loss of bands from SDS gels corresponding to sequenced material. Bacterial lipopolysaccharide (which forms high-affinity complexes with LBP) specifically neutralized the cofactor activity of the LBP preparation in a concentration-dependent manner. Bovine serum and plasma, as well as the C4BP preparation, optimally supported the binding of a rabbit anti-C4BP antiserum to immobilized cardiolipin. The binding of a rabbit anti-AT antiserum to solid-phase cardiolipin was sustained by the thrombin-AT preparation and bovine serum, but neither by bovine plasma nor by native AT, thus reproducing the behavior of patient no. 6 ACA. Taking advantage of the restricted recognition by the latter ACA of a cofactor from bovine origin appearing upon clotting, we studied the generation of such activity in human plasma supplemented with bovine AT or bovine prothrombin before clotting. In these conditions, patient no. 6 antibody binding to cardiolipin required the addition of bovine AT, whereas addition of bovine prothrombin alone was ineffective. We therefore concluded that those ACA targeted bovine AT once it has been modified/cleaved by thrombin. These findings underline the wide heterogeneity of ACA and the links that may exist between various coagulation pathways, inflammation and the complement system.

Some Anticardiolipin Antibodies Recognize a Combination of Phospholipids With Thrombin-Modified Antithrombin, Complement C4b-Binding Protein, and Lipopolysaccharide Binding Protein

Blood ◽  
1999 ◽  
Vol 93 (12) ◽  
pp. 4248-4255
Author(s):  
Josiane Arvieux ◽  
Gilles Pernod ◽  
Véronique Regnault ◽  
Luc Darnige ◽  
Jérôme Garin
Keyword(s):  
Bovine Serum ◽  
Binding Protein ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Deae Cellulose ◽  
Anticardiolipin Antibodies ◽  
Enzyme Linked Immunosorbent Assay ◽  
Dependent Manner ◽  
Lipopolysaccharide Binding Protein ◽  
Lipopolysaccharide Binding

The standard enzyme-linked immunosorbent assay (ELISA) for anticardiolipin antibodies (ACA) detects a heterogenous group of antibodies against cardiolipin on its own, β2-glycoprotein I (β2GPI), and, potentially, other phospholipid-binding plasma proteins from bovine or human origin. In an attempt to identify new proteic targets of ACA, we selected 6 patients who possessed cofactor-dependent ACA but no antibody to human or bovine β2GPI detectable in the β2GPI-ELISA. Three of these samples proved to recognize β2GPI in combination with cardiolipin, but not β2GPI directly immobilized on γ-irradiated polystyrene or agarose beads. In the other cases, the component required for ACA binding was purified from adult bovine serum or plasma by means of ammonium sulfate precipitation and chromatography on Phenyl-Sepharose, diethyl aminoethyl (DEAE)-cellulose, heparin-Ultrogel, and Sephacryl S-300 columns. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis coupled to N-terminal amino acid microsequencing identified the cofactors of patients no. 4, 5, and 6 ACA as lipopolysaccharide binding protein (LBP), complement C4b-binding protein (C4BP), and the thrombin-antithrombin (AT) complex, respectively. Adsorption of each of these cofactor preparations with cardiolipin liposomes led to suppression of ACA reactivity, concomitant with the loss of bands from SDS gels corresponding to sequenced material. Bacterial lipopolysaccharide (which forms high-affinity complexes with LBP) specifically neutralized the cofactor activity of the LBP preparation in a concentration-dependent manner. Bovine serum and plasma, as well as the C4BP preparation, optimally supported the binding of a rabbit anti-C4BP antiserum to immobilized cardiolipin. The binding of a rabbit anti-AT antiserum to solid-phase cardiolipin was sustained by the thrombin-AT preparation and bovine serum, but neither by bovine plasma nor by native AT, thus reproducing the behavior of patient no. 6 ACA. Taking advantage of the restricted recognition by the latter ACA of a cofactor from bovine origin appearing upon clotting, we studied the generation of such activity in human plasma supplemented with bovine AT or bovine prothrombin before clotting. In these conditions, patient no. 6 antibody binding to cardiolipin required the addition of bovine AT, whereas addition of bovine prothrombin alone was ineffective. We therefore concluded that those ACA targeted bovine AT once it has been modified/cleaved by thrombin. These findings underline the wide heterogeneity of ACA and the links that may exist between various coagulation pathways, inflammation and the complement system.

Mechanism of Action of a Potent Antiplatelet Peptide, Triflavin from Trimeresurus flavoviridis Snake Venom

1991 ◽  
Vol 66 (04) ◽  
pp. 489-493 ◽  
Author(s):  
Tur-Fu Huang ◽  
Joen-Rong Sheu ◽  
Che-Ming Teng
Keyword(s):  
Snake Venom ◽  
Shape Change ◽  
Membrane Surface ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Free Calcium ◽  
Activation Process ◽  
Trimeresurus Flavoviridis ◽  
Fibrinogen Binding ◽  
Induced Aggregation

SummaryTriflavin, an antiplatelet peptide from Trimeresurus flavoviridis snake venom, inhibits aggregation of human platelets stimulated by a variety of agonists. However, triflavin does not affect the shape change and release reaction of platelets stimulated by thrombin and collagen. In this paper, we further investigate its effect on the intracellular events occurring after the activation of platelets. Triflavin does not inhibit the intracellular free calcium rise of Quin 2-AM loaded platelets stimulated by thrombin and it also has no significant effect on thromboxane B2 formation of platelets stimulated by thrombin. Triflavin does not affect the 3(H)-inositol monophosphate formation of the 3(H)-myoinositol loaded platelets. However, triflavin dose-dependently inhibits fibrinogen-induced aggregation and 125I-fibrinogen binding of ADP-stimulated platelets. In addition, triflavin dose-dependently blocks fibrinogen-induced aggregation of elastase-treated platelets. It is concluded that triflavin specifically inhibits fibrinogen binding to fibrinogen receptors associated with glycoprotein IIb/IIIa complex on platelet membrane surface without any inhibitory effect on the platelet-activation process.

Sign in / Sign up

Export Citation Format

Share Document