Effect of Prostacyclin (Epoprostenol) on the Aggregation of Human Platelets in Whole Blood in vitro

1984 ◽  
Vol 14 (6) ◽  
pp. 487-494
Author(s):  
A.R. Saniabadi ◽  
G.D.O. Lowe ◽  
J.J.F. Belch ◽  
J.C. Barbenel ◽  
C.D. Forbes
Keyword(s):  
Whole Blood ◽  
Human Platelets

Endotoxin-Induced Platelet Activation in Human Whole Blood In Vitro

1988 ◽  
Vol 59 (03) ◽  
pp. 378-382 ◽  
Author(s):  
Gyorgy Csako ◽  
Eva A Suba ◽  
Ronald J Elin
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Atp Release ◽  
Human Platelets ◽  
Lag Phase ◽  
Human Whole Blood ◽  
Dose Dependent

SummaryThe effect of purified bacterial endotoxin was studied on human platelets in vitro. In adding up to 1 μg/mL of a highly purified endotoxin, we found neither aggregation nor ATP release in heparinized or citrated human platelet-rich plasma. On the other hand, endotoxin at concentrations as low as a few ng/mL (as may be found in septic patients) caused platelet aggregation in both heparinized and citrated human whole blood, as monitored by change in impedance, free platelet count, and size. Unlike collagen, the platelet aggregation with endotoxin occurred after a long lag phase, developed slowly, and was rarely coupled with measurable release of ATP. The platelet aggregating effect of endotoxin was dose-dependent and modified by exposure of the endotoxin to ionizing radiation. Thus, the activation of human platelets by “solubilized” endotoxin in plasma requires the presence of other blood cells. We propose that the platelet effect is mediated by monocytes and/or neutrophils stimulated by endotoxin.

scholarly journals Comparative Studies of Platelet Survival by Different Methods in the Rabbit

Blood ◽  
1965 ◽  
Vol 25 (4) ◽  
pp. 548-566 ◽  
Author(s):  
SHIRLEY EBBE ◽  
MARIO BALDINI ◽  
JANET DONOVAN
Keyword(s):  
Survival Time ◽  
Whole Blood ◽  
Comparative Studies ◽  
Significant Degree ◽  
Human Platelets ◽  
Sodium Chromate ◽  
Platelet Concentrates ◽  
Rabbit Platelets

Abstract Four methods for measuring the survival of homologous platelets in rabbits were studied: (1) transfusion of nonradioactive platelet concentrates to thrombocytopenic recipients, (2) transfusion of concentrates of platelets labeled in vitro with Cr51-sodium chromate, (3) transfusion of concentrates of platelets labeled in vivo with P32-orthophosphate and (4) transfusion of whole blood labeled in vivo with P32-orthophosphate. The survival time of platelets in normal rabbits was 3-4 days. From comparison of the 3 methods using platelet concentrates, the following conclusions were drawn. (1) All the platelets in a platelet concentrate were capable of recirculating after transfusion. (2) Labeling with P32 or Cr51 did not damage platelets. (3) About one-third of the Cr51 was immediately eluted from viable platelets after they were transfused. (4) Further exchange of the label in vivo did not occur to a significant degree with either Cr51 or P32. (5) Cr51 did not elute from platelets during storage of the platelets. (6) Studies of rabbit platelets had applicability in predicting the behavior of human platelets.

The Use of Monoclonal Antibodies to Human Platelet Membrane Glycoprotein IIb-IIIa to Quantitate Platelet Deposition on Artificial Surfaces

1987 ◽  
Vol 58 (02) ◽  
pp. 724-731 ◽  
Author(s):  
Juliette N Mulvihill ◽  
Han G Huisman ◽  
Jean-Pierre Cazenave ◽  
Jan A van Mourik ◽  
Willem G van Aken
Keyword(s):  
Whole Blood ◽  
Human Albumin ◽  
Human Platelets ◽  
Membrane Glycoprotein ◽  
Bovine Collagen ◽  
Glass Capillaries ◽  
Platelet Deposition ◽  
A New Technique ◽  
Albumin Adsorption

SummaryA new technique is described to quantitate platelet deposition in vitro on artifical surfaces, based on a surface phase radioimmunoassay using the monoclonal antibody 6C9, directed specifically against the membrane glycoprotein complex IIb-IIIa of human platelets. Results correlate in linear fashion with those obtained using 111Indium labeled platelets. The method offers particular advantages for the measurement of platelet deposition in whole blood, since platelet separation, washing and labeling procedures are eliminated, together with the ensuing possible selection of platelet populations. In vitro perfusion is performed in glass capillaries of precisely defined diameter (0.80 or 0.56 mm i.d.). Blood flow is laminar and accurately controlled over wall shear rates ranging from venous to capillary (50-4,000 s-1). Using glass capillaries precoated with purified human albumin or fibrinogen or bovine collagen, platelet deposition from suspensions of washed human platelets in Tyrode's-albumin buffer in the presence of a 40% hematocrit is (platelets/mm2): 11,000 (albumin), 78,000 (fibrinogen) and 306,000 (collagen) after 5 min perfusion at 2,000 s-1. In heparin, citrate or hirudin anticoagulated whole blood, surfaces are passivated, probably by albumin adsorption from plasma (platelets/mm2): 400 (albumin), 3,600 (fibrinogen) and 48,000 (collagen) after 5 min perfusion in the presence of 13 mM citrate.

Clopidogrel inhibits platelet-leukocyte adhesion and plateletdependent leukocyte activation

2005 ◽  
Vol 94 (09) ◽  
pp. 568-577 ◽  
Author(s):  
Stefano Manarini ◽  
Giuseppe Dell’Elba ◽  
Nicola Martelli ◽  
Emanuela Napoleone ◽  
Angelomaria Di Santo ◽  
...  
Keyword(s):  
Whole Blood ◽  
Active Metabolite ◽  
Polymorphonuclear Leukocytes ◽  
Ex Vivo ◽  
Leukocyte Adhesion ◽  
Human Platelets ◽  
Cell System ◽  
Anti Platelet Therapy ◽  
Acute Complications

SummaryClopidogrel is considered to be an important therapeutic advance in anti-platelet therapy. We investigated whether inhibition by clopidogrel results in a reduced capacity of platelets to adhere and stimulate pro-atherothrombotic and inflammatory functions in polymorphonuclear leukocytes (PMN) and in monocytes (MN). An eventual effect on these processes could further substantiate anti-atherothrombotic properties of this drug. The effects of clopidogrel or of its active metabolite were investigated on ADP or thrombin receptor-induced platelet activation and on platelet-leukocyte interactions ex vivo in the mouse or in vitro in isolated human cells or whole blood, respectively. Clopidogrel inhibited platelet aggregation, expression of P-selectin, platelet-PMN adhesion and platelet-dependent ROS production in mouse PMN. Similarly pretreatment of human platelets with the active metabolite of clopidogrel in vitro resulted in a profound inhibition of platelet P-selectin expression, platelet-PMN adhesion and production of ROS by PMN. Pretreatment with the active metabolite of clopidogrel significantly impaired the ability of platelets to up-regulate the expression of TF procoagulant activity in MN, in a washed cell system. Moreover, the active metabolite of clopidogrel inhibited rapidTF exposure on platelet as well as on leukocyte surfaces in whole blood. By reducing platelet-dependent up-regulation of inflammatory and pro-atherothrombotic functions in leukocytes, clopidogrel may reduce inflammation that underlies the chronic process of atherosclerosis and its acute complications.

A Radioimmunoassay for Human Platelet β-Thromboglobulin

1975 ◽  
Author(s):  
C. A. Ludlam ◽  
A. E. Bolton
Keyword(s):  
Whole Blood ◽  
Heart Valves ◽  
Plasma Concentrations ◽  
Human Platelets ◽  
Prosthetic Heart Valves ◽  
Platelet Poor Plasma ◽  
Release Reaction ◽  
Assay Conditions

β-thromboglobulin (βtg) is a protein recently isolated from human platelets. A radioimmunoassay for βtg has been established.Using this assay, conditions have been defined for the preparation of platelet poor plasma, so as to minimise the liberation of βtg during manipulations in vitro. Platelet poor plasma prepared from whole blood, collected in EDTA, prostaglandin E9, and theophylline, and centrifuged at 0°C., contained 0.019±0.0075 μg ml−1 (mean±l SD). Serum prepared from clotted whole blood (in which platelets had undergone the release reaction) had a concentration of 17.4±6.3 μg ml−1, while plasma from platelet transfusion concentrates contained 247.0±120.3 μg ml−1. There was no increase in βtg concentration when platelet poor plasma was clotted by the addition of calcium. The presence of a 1000-fold difference between plasma and serum concentrations, the observed release following collagen induced platelet aggregation in vitro, and the observations that other human tissues contained only trace amounts suggests that βtg is unique to platelets.Preliminary clinical studies have shown that patients with acute arterial thrombosis and others with prosthetic heart valves have raised plasma concentrations. It is possible, therefore, that this assay has potential uses for studying the platelet release reaction in vitro, and also the identification of individuals with excessive platelet sequestration in vivo.

R 68 070: Thromboxane A2 Synthetase Inhibition and Thromboxane A2/Prostaglandin Endoperoxide Receptor Blockade Combined in One Molecule - I. Biochemical Profile In Vitro

1989 ◽  
Vol 61 (01) ◽  
pp. 035-042 ◽  
Author(s):  
F De Clerck ◽  
J Beetens ◽  
D de Chaffoy de Courcelles ◽  
E Freyne ◽  
P A J Janssen
Keyword(s):  
Arachidonic Acid ◽  
Whole Blood ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Thromboxane A2 ◽  
Human Platelets ◽  
Receptor Blockade ◽  
Biochemical Profile ◽  
Prostaglandin Endoperoxide

SummaryR 68 070 or (E)-5-[[[(3-pyridinyl)[3-(trifluoromethyl)phenyl]- methylen]amino]oxy] pentanoic acid (Janssen Research Foundation, Belgium) combines specific thromboxane A2 (TXA2) synthetase inhibition with TXA2/prostaglandin endoperoxide receptor blockade in one molecule.In vitro, the compound specifically inhibits the production of TXB2 from [14C] arachidonic acid by washed human platelets (IC50 = 8.2 × 10-9 M) and by platelet microsomes (IC50 = 3.6 × 10-9 M), of MDA (IC50 = 1.91 × 10-8 M) and of TXB2 (IC50 = 1.47 × 10-8 M) by thrombin-coagulated human platelet-rich plasma (P.R.P.) and whole blood respectively and increases the levels of PGD2, PGE2, PGF2α and 6-keto-PGF1α. The activity of cyclo-oxygenase-, prostacyclin synthetase-, 5-, 12- and 15-lipoxygenase-enzymes are not affected. Additionally, R 68 070 inhibits human platelet aggregation in P.R.P. induced by U 46619 3 × 10-7 M to 2 × 10-6 M (IC50 = 2.08 × 10-6 M to 2.66 × 10-5 M), collagen 0.5 to 2 μg/ml (IC50 = 2.85 × 10-6 M to 4.81 × 10-5 M), arachidonic acid 7.5 × 10-4 M to 2 × 10- M (IC50 = 2.1 × 10-8 M to 3.3 × 10-8 M) and the U 46619 (1 × 10-7 M)-induced accumulation of [32P] phosphatidic acid (IC50 = 5.24 × 10-7 M) in washed human platelets. Collagen (0.75 μg/ml)-induced ATP release (IC50 = 4.1 × 10-6 M), ADP (1 to 2.5 × 10-6 M)-induced second wave aggregation (IC50 = 3.19 × 10-6 M) in P.R.P. as well as the collagen (1 μg/ml)-induced adhesion/aggregation reaction in human whole blood (IC50 = 1.02 × 10-5 M) are reduced as well by the compoun.Primary platelet reactions induced by serotonin, ADP, PAF, or A 23187, platelet adenylate cyclase- and cAMP phosphodiesterase-activity, and platelet inhibitory activities of PGD2, PGI2, PGE2, PGE1 are not modified by R 68 070.This biochemical profile is compatible with a dual mechanism of action of R 68 070, namely TXA2 synthetase inhibition at low concentrations, plus additionally TXA2/prostaglandin endoperoxide receptor blockade at higher concentrations

Serotonergic mechanisms enhance platelet-mediated thrombogenicity

2009 ◽  
Vol 102 (09) ◽  
pp. 511-519 ◽  
Author(s):  
Irene Lopez-Vilchez ◽  
Maribel Diaz-Ricart ◽  
Fulgencio Navalon ◽  
Esther Gomez ◽  
Cristobal Gasto ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Whole Blood ◽  
Thrombin Generation ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Selective Inhibition ◽  
Human Platelets ◽  
Experimental Conditions ◽  
Perfusion Studies

SummaryAlthough it is generally acknowledged that serotonin (5-HT) is a weak agonist for human platelets, recent information suggests an association between serotonergic mechanisms and cardiovascular risk. We investigated the action of 5-HT on adhesive, cohesive and procoagulant properties of human platelets. Impact of 5-HT on whole blood coagulation and thrombin generation was measured by modified thromboelastometry (TEM) and specific fluorogenic assays. We evaluated the effects of 5-HT on thrombus formation in an in-vitro model of thrombosis using human flowing blood. In platelet-rich plasma (PRP), 5-HT favoured the expression of CD62-P, and procoagulant molecules on platelet membranes. These effects were potentiated in the presence of Ca++ and/or ADP. Incubation with 5-HT accelerated clotting times and augmented clot strength in whole blood TEM, and enhanced thrombin generation in PRP. In perfusion studies, 5-HT significantly increased fibrin deposition at low shear (300s-1) and enhanced platelet thrombus formation on the damaged vascular surface at high shear (1,200s-1). Selective inhibition of serotonin reuptake (SSRI) attenuated effects of 5-HT on platelet activation and downregulated the prothrombotic tendencies observed in the previous experimental conditions. In general, reductions of thrombogenic patterns observed with SSRI were more evident under shear conditions (aggregation and perfusion systems) and less evident under steady conditions (TEM and thrombin generation assays). In conclusion, 5-HT is not a weak agonist for human platelets; instead it accentuates platelet activation, potentiates procoagulant responses on human blood and increases thrombogenesis on damaged vascular surfaces. The remarkable antithrombotic actions achieved through SSRI deserve further mechanistic and clinical investigations.

Increased Protein Synthesis by Human Platelets during Phagocytosis of Latex Particles in Vitro

1976 ◽  
Vol 35 (02) ◽  
pp. 350-357 ◽  
Author(s):  
Hana Bessler ◽  
Galila Agam ◽  
Meir Djaldetti
Keyword(s):  
Protein Synthesis ◽  
Fold Increase ◽  
Human Platelets ◽  
Polystyrene Latex ◽  
Latex Particles ◽  
The Third ◽  
Platelet Protein ◽  
Dose Dependent ◽  
Phagocytotic Activity

SummaryA three-fold increase of protein synthesis by human platelets during in vitro phagocytosis of polystyrene latex particles was detected. During the first two hours of incubation, the percentage of phagocytizing platelets and the number of latex particles per platelet increased; by the end of the third hour, the first parameter remained stable, while the number of latex particles per cell had decreased.Vincristine (20 μg/ml of cell suspension) inhibited platelet protein synthesis. This effect was both time- and dose-dependent. The drug also caused a decrease in the number of phagocytizing cells, as well as in their phagocytotic activity.

Effect of Dipyridamole on Spontaneous Platelet Aggregation in Whole Blood Decreases with the Time After Venepuncture: Evidence for the Role of ADP

1987 ◽  
Vol 58 (02) ◽  
pp. 744-748 ◽  
Author(s):  
A R Saniabadi ◽  
G D O Lowe ◽  
J C Barbenel ◽  
C D Forbes
Keyword(s):  
Platelet Aggregation ◽  
Correlation Coefficient ◽  
Whole Blood ◽  
Blood Platelet ◽  
Inhibitory Effect ◽  
Time Interval ◽  
Adp Receptor ◽  
Spontaneous Platelet Aggregation

SummarySpontaneous platelet aggregation (SPA) was studied in human whole blood at 3, 5, 10, 20, 30, 40 and 60 minutes after venepuncture. Using a whole blood platelet counter, SPA was quantified by measuring the fall in single platelet count upon rollermixing aliquots of citrated blood at 37° C. The extent of SPA increased with the time after venepuncture, with a correlation coefficient of 0.819. The inhibitory effect of dipyridamole (Dipy) on SPA was studied: (a) 10 μM at each time interval; (b) 0.5-100 μM at 3 and 30 minutes and (c) 15 μM in combination with 100 μM adenosine, 8 μM 2-chloroadenosine (2ClAd, an ADP receptor blocker) and 50 μM aspirin. There was a rapid decrease in the inhibitory effect of Dipy with the time after venepuncture; the correlation coefficient was -0.533. At all the concentrations studied, Dipy was more effective at 3 minutes than at 30 minutes after venepuncture. A combination of Dipy with adenosine, 2ClAd or aspirin was a more effective inhibitor of SPA than either drug alone. However, when 15 μM Dipy and 10 μM Ad were added together, the inhibitory effect of Dipy was not increased significantly, suggesting that Dipy inhibits platelet aggregation independent of Ad. The increase in SPA with the time after venepuncture was abolished when blood was taken directly into the anticoagulant containing 5 μM 2ClAd. It is suggested that ADP released from the red blood cells is responsible for the increased platelet aggregability with the time after venepuncture and makes a serious contribution to the artifacts of in vitro platelet function studies.

Sign in / Sign up

Export Citation Format

Share Document