Platelet Shape Change in Whole Blood: Differential Effects of Endotoxin

1994 ◽  
Vol 71 (05) ◽  
pp. 646-650 ◽  
Author(s):  
M L Nystrom ◽  
M A Barradas ◽  
J Y Jeremy ◽  
D P Mikhailidis
Keyword(s):  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Platelet Activating Factor ◽  
Final Concentration ◽  
Platelet Volume ◽  
Differential Effects ◽  
Platelet Shape

SummaryThe effect of endotoxic lipopolysaccharide (LPS) on platelet shape change (PSC; a preaggregation event) was investigated. PSC is accompanied by an increase in median platelet volume (MPV), which was measured using a channelyzer. In whole blood, but not in platelet rich plasma (PRP), LPS (final concentration 80 mg/1) caused an increase in MPV that could be detected for 2 h. When PRP (prepared from LPS- and saline-pretreated whole blood) was incubated for 40 min, the LPS-mediated increase in MPV could no longer be detected. Taken together, these data imply that PSC is both initiated and maintained by a labile factor(s) present in whole blood, but not in PRP.PRP was prepared from LPS-pretreated whole blood and incubated for 40 min to allow reversal of the LPS-induced PSC; further stimulation with LPS caused PSC. Platelets from LPS-pretreated whole blood also showed enhanced PSC with seioloum (J-HT), diminished PSC with platelet activating factor (PAF), and no change of response to ADP and collagen. Hence, LPS pretreatment of whole blood differentially alters responses of platelets to further stimulation with LPS and other agonists. A specific PAF antagonist completely abolished the effect of LPS on MPV. These data may contribute to an understanding of the cascading thrombotic events and thrombocylopeuia assoeialed wiib septicaemia.

scholarly journals The Effect of Tirofiban on Fibrinogen/Agonist-Induced Platelet Shape Change and Aggregation

2008 ◽  
Vol 14 (3) ◽  
pp. 295-302 ◽  
Author(s):  
I. Anita Jagroop ◽  
Dimitri P. Mikhailidis
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Adenosine Diphosphate ◽  
Vascular Events ◽  
Spontaneous Platelet Aggregation ◽  
Induced Aggregation ◽  
Platelet Shape

There is evidence linking raised plasma fibrinogen (fib) and platelet hyperactivity with vascular events. One way to inhibit platelets is to block the platelet membrane glycoprotein (GP) IIb/IIIa receptor, which binds circulating fib or von Willebrand factor and cross-links platelets at the final common pathway to platelet aggregation. Tirofiban is a potent and specific fib receptor antagonist, used in the treatment of unstable angina. The authors assessed the effect of tirofiban on spontaneous platelet aggregation (SPA), fib-induced, serotonin (5HT)-induced, and adenosine diphosphate (ADP)-induced aggregation in whole blood by calculating the percentage free platelet count. These various agonists were used alone and in combination. The authors also measured the effect of tirofiban on agonists-induced (ADP, 5HT) platelet shape change (PSC). The effect of fib on PSC was also evaluated in platelet-rich plasma using a high-resolution (0.07 fL) channelyzer. Tirofiban significantly inhibited SPA, fib (2, 4, 8 g/L), ADP, ADP + fib combination, and 5HT-induced aggregation. Tirofiban had no effect on agonist-induced PSC. There was no apparent change in platelet volume with fib. In conclusion, tirofiban does not appear to have an effect on PSC, an early phase of platelet activation. Tirofiban seems to be a nonspecific and an effective inhibitor of platelet aggregation (a later phase of platelet activation) in whole blood. The clinical significance of these findings remains to be established.

Platelet Volume Measurements: The Importance Of Anticoagulation

1981 ◽  
Author(s):  
C B Thompson ◽  
D D Diaz ◽  
P G Quinn ◽  
M Lapins ◽  
S B Kurtz ◽  
...  
Keyword(s):  
Platelet Count ◽  
Whole Blood ◽  
Mean Platelet Volume ◽  
Room Temperature ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Inverse Correlation ◽  
Platelet Volume ◽  
Important Indicator ◽  
Platelet Counts

Recent advances in electrical cell sizing have made mean platelet volume (MPV) routinely available in most clinical laboratories. To study the importance of anticoagulation on platelet size stability, blood was collected in 7 different anticoagulants and stored at room temperature for up to 8 hours. Platelet counts and platelet sizing were performed using whole blood on a Coulter S+ and using platelet-rich plasma on a Coulter H4 Channelyzer. The results suggest that both calcium chelation and acidification were required to inhibit platelet shape change and aggregation. Electrolyte composition, pH, and tonicity of the anticoagulant all influenced the stability of the MPV. As a result of these studies, an anticoagulant combining ACD and Na2EDTA at a pH of 5.0 and an osmotic strength of 308 m0sm/1 was used to study platelet volume and counts in whole blood on a Coulter S+ used in the hematology laboratory of our hospital. Platelet counts with ACD-Na2EDTA anticoagulant were no different from routine Na2EDTA platelet counts and exhibited 2.9% error in reproducibility and a 4.4% variability over the 8 hours of storage. Mean platelet volumes were reproducible to within 3% and had less than 1% variability over the 8 hours of storage. Platelets anticoagulated with ACD-Na2EDTA remained discoid in shape and could be shown to undergo a shape change on stimulation with ADP up to at least 8 hours after collection, when the pH was adjusted to 7.4 and the Ca++ concentration restored.These data demonstrate that platelet count and platelet volumes remained stable in blood collected in ACD-Na2EDTA anticoagulant for up to 8 hours at room temperature. In 52 volunteers studied, an inverse correlation (r=.72, p<0.001) was observed between platelet count and MPV, suggesting that the circulating platelet mass may be a more important indicator of platelet homeostasis than either the platelet count or the mean platelet volume alone.

The plaque lipid lysophosphatidic acid stimulates platelet activation and platelet-monocyte aggregate formation in whole blood: involvement of P2Y1 and P2Y12 receptors

Blood ◽  
2004 ◽  
Vol 103 (7) ◽  
pp. 2585-2592 ◽  
Author(s):  
Nadine Haserück ◽  
Wolfgang Erl ◽  
Dharmendra Pandey ◽  
Gabor Tigyi ◽  
Philippe Ohlmann ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Lysophosphatidic Acid ◽  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Receptor Activation ◽  
Aggregate Formation ◽  
Serotonin Secretion ◽  
Induced Aggregation ◽  
Platelet Shape

Abstract Despite the fact that lysophosphatidic acid (LPA) has been identified as a main platelet-activating lipid of mildly oxidized low-density lipoprotein (LDL) and human atherosclerotic lesions, it remains unknown whether it is capable of activating platelets in blood. We found that LPA at concentrations slightly above plasma levels induces platelet shape change, aggregation, and platelet-monocyte aggregate formation in blood. 1-alkyl-LPA (16:0 fatty acid) was almost 20-fold more potent than 1-acyl-LPA (16:0). LPA directly induced platelet shape change in blood and platelet-rich plasma obtained from all blood donors. However, LPA-stimulated platelet aggregation in blood was donor dependent. It could be completely blocked by apyrase and antagonists of the platelet adenosine diphosphate (ADP) receptors P2Y1 and P2Y12. These substances also inhibited LPA-induced aggregation of platelet-rich plasma and aggregation and serotonin secretion of washed platelets. These results indicate a central role for ADP-mediated P2Y1 and P2Y12 receptor activation in supporting LPA-induced platelet aggregation. Platelet aggregation and platelet-monocyte aggregate formation stimulated by LPA was insensitive to inhibition by aspirin. We conclude that LPA at concentrations approaching those found in vivo can induce platelet shape change, aggregation, and platelet-monocyte aggregate formation in whole blood and suggest that antagonists of platelet P2Y1 and P2Y12 receptors might be useful preventing LPA-elicited thrombus formation in patients with cardiovascular diseases.

Time Dependence of Whole Blood Aggregation in Response to Platelet Activating Factor (PAF)

1988 ◽  
Vol 59 (02) ◽  
pp. 162-163 ◽  
Author(s):  
R R Taylor ◽  
J Strophair ◽  
M Sturm ◽  
R Vandongen ◽  
L J Beilin
Keyword(s):  
Time Dependence ◽  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Platelet Activating Factor ◽  
Sampling Time ◽  
Blood Sampling ◽  
Impedance Aggregometry

SummaryThe aggregation/adhesion response to platelet activating factor (PAF) was studied in diluted whole blood by impedance aggregometry. The extent of aggregation varied directly with the interval between blood sampling and aggregation measurement over the first 30 minutes from sampling, then remained stable for the next 60 minutes of observation. This is an effect opposite to that described for aggregation to PAF in platelet rich plasma which, however, cannot be studied soon after sampling. Time dependence of aggregation is important and comparative measurements should be made during the period of stable aggregability.

Adenosine Diphosphate (ADP)-Induced ⍺-Granules Release from Platelets of Native Whole Blood Is Reduced by Ticlopidine but Not by Aspirin or Dipyridamole

1986 ◽  
Vol 56 (02) ◽  
pp. 147-150 ◽  
Author(s):  
V Pengo ◽  
M Boschello ◽  
A Marzari ◽  
M Baca ◽  
L Schivazappa ◽  
...  
Keyword(s):  
Whole Blood ◽  
Light Transmission ◽  
Ex Vivo ◽  
Early Stage ◽  
Shape Change ◽  
Adenosine Diphosphate ◽  
Dose Dependent ◽  
Plateletderived Growth Factor ◽  
Platelet Shape

SummaryA brief contact between native whole blood and ADP promotes a dose-dependent release of platelet a-granules without a fall in the platelet number. We assessed the “ex vivo” effect of three widely used antiplatelet drugs, aspirin dipyridamole and ticlopidine, on this system. Aspirin (a single 800 mg dose) and dipyridamole (300 mg/die for four days) had no effect, while ticlopidine (500 mg/die for four days) significantly reduced the a-granules release for an ADP stimulation of 0.4 (p <0.02), 1.2 (p <0.01) and 2 pM (p <0.01). No drug, however, completeley inhibits this early stage of platelet activation. The platelet release of α-granules may be related to platelet shape change of the light transmission aggregometer and may be important “in vivo” by enhancing platelet adhesiveness and by liberating the plateletderived growth factor.

ADP-induced inhibition of von Willebrand factor-mediated platelet agglutination

1976 ◽  
Vol 230 (5) ◽  
pp. 1406-1410 ◽  
Author(s):  
RA Grant ◽  
MB Zucker ◽  
J McPherson
Keyword(s):  
Human Plasma ◽  
Von Willebrand Factor ◽  
Prostaglandin E1 ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Normal Human ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Formalin Fixed ◽  
Platelet Shape

Human plasma von Willebrand factor (vWF) plus the antibiotic ristocetin, or bovine or porcine vWF alone, agglutinates platelets in either normal human ethylenediaminetetraacetate (EDTA)-treated citrated platelet-rich plasma (PRP) or citrated PRP from patients with the congenital platelet defect thrombasthenia. The prior addition of 1-10 muM ADP, which causes platelet shape change but not aggregation under these conditions, inhibited vWF-mediated agglutination. Inhibition was prevented by 200 muM ATP. Addition of ADP caused prompt reversal of established vWF-mediated agglutination, which resumed when the ADP was enzymatically removed. EDTA-treated, Formalin-fixed, washed normal platelets also underwent vWF-mediated agglutination. ADP was inhibitory only when added before fixation. Epinephrine (40 muM), prostaglandin E1 (7 muM), or serotonin (2 muM) added before fixation caused slight to moderate inhibition but always less than ADP. Platelets from blood chilled before fixation were fully active. Platelets fixed in freshly prepared PRP did not agglutinate as well as those fixed after incubation of PRP, probably because centrifugation exposes the platelets to ADP. It concluded that ADP causes a reversible decrease in the accessibility of the membrane receptor to vWF.

Altered Platelet Shape Change in Hereditary Gelsolin Asp187Asn-related Amyloidosis

2000 ◽  
Vol 83 (03) ◽  
pp. 491-495 ◽  
Author(s):  
Kaija Javela ◽  
Hannu Somer ◽  
Riitta Kekomäki ◽  
Sari Kiuru
Keyword(s):  
Factor Viii ◽  
Light Transmission ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Coagulation Factor ◽  
Coagulation Factor Viii ◽  
Bleeding Tendency ◽  
Knock Out ◽  
Ristocetin Cofactor ◽  
Platelet Shape

SummaryHereditary gelsolin-related amyloidosis (AGel amyloidosis) is a systemic disorder caused by a G654A or G654T mutation in the gene coding for gelsolin, an actin-modulating protein. Altered platelet shape change has been demonstrated in gelsolin-deficient knock-out mice, but this has not been studied in humans with gelsolin deficiency. We measured platelet shape change, characterized by maximal decrease in light transmission (D) and reaction time (T), and aggregation, associated with stimulation of platelets with different agonists in platelet rich plasma, as well as coagulation factor VIII and ristocetin cofactor activities in 20 patients, 10 healthy sibs and 20 healthy control subjects. Statistically significant alterations of parameters describing platelet shape change (D, T) were observed after stimulation with adenosine diphosphate and collagen in patients when compared to healthy subjects, but not in maximal aggregation responses, platelet counts, coagulation factor VIII or ristocetin cofactor activity levels. Patients had more haemostatic derangements. Our results suggest that, in addition to amyloid deposition, the G654A gelsolin gene defect causes altered gelsolin-mediated cellular mechanisms, which may contribute, e. g., to bleeding tendency in AGel amyloidosis patients.

scholarly journals Mechanism of Action of Halofenate, A Platelet Inhibitor

1977 ◽  
Author(s):  
G. R. Favis ◽  
R. W. Colman
Keyword(s):  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Thiobarbituric Acid ◽  
Serotonin Release ◽  
Prostaglandin Synthesis ◽  
Second Phase ◽  
Change Curve ◽  
Cellulose Column ◽  
Platelet Shape

Halofenate (Hal) has previously been shown to inhibit epinephrine (Epi) and ADP induced platelet aggregation and C14-serotonin release. We further investigated the site of action of Hal by examining platelet shape change as a membrane event and malondialdehyde (MDA) formation as a measure of prostaglandin synthesis. Platelet-rich-plasma (PRP) with and without Hal wasdiluted in an EDTA buffer and examined in a spectrophotometer modified for stirring and maintained at 37°. ADP induced increase in absorbance was recorded and the velocity of the shape change curve was plotted against ADP concentration. MDA production was measured by the thiobarbituric acid assay and utilized a DEAE-52 cellulose column to concentrate the chromogen. Hal in pharmacologic concentrations (.96mM) had no effect on Epi induced primary aggregation or on ADP induced shape change. However, at higher than pharmacologic amounts (3.36mM), Hal did inhibit ADP induced shape change. Epi-induced MDA formation (.18μM-.33μM) normally occurs concomitant with the second phase of aggregation and serotonin release but was markedly decreased by Hal (.06μM-.085μM). This inhibition was not due to a direct effect on prostaglandin synthesis since sodium arachi-donate (1mM) caused secondary aggregation in PRP treated with Hal but not PRP treated with aspirin (4mM). Hal (.96mM) does not seem to inhibit platelet aggregation through an inhibition of ADP induced shape change or of Epi induced primary aggregation. Since Hal treated platelets respond to arachidonate, Hal must work at some earlier step than arachidonate induced prostaglandin synthesis. We suggest that this may be an alteration of the platelet membrane structure which makes ADP and Epi binding sites less accessible or which impairs arachidonic acid release by phospholipase. Decreased MDA formation and inhibition of aggregation would then be secondary to this membrane change.

Possible Differences In The Mode Of Action Of Ditazole And Non-Steroidal Anti-Inflammatory Drugs As Potential Antithrombotic Agents

1981 ◽  
Author(s):  
A K Sim ◽  
A P McCraw ◽  
L Caprino ◽  
F Antonetti ◽  
L Morelli
Keyword(s):  
Platelet Aggregation ◽  
Mode Of Action ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Dose Range ◽  
Oral Drug ◽  
Inflammatory Drugs ◽  
Anti Inflammatory ◽  
Induced Aggregation ◽  
Platelet Shape

Ditazole (4,5-diphenyl-2-diethanolamino-oxazole), a weak anti-inflammatory drug, has been shown to be a potent inhibitor of platelet aggregation, adhesiveness and bleeding time. Acetylsalicylic acid (ASA), dipyridamole and a combination of these two drugs induced a platelet shape change which was much shorter lasting than their effect on platelet aggregation. Conversely, similar doses of ditazole induced a potent shape change but no effect on aggregation. Ditazole has now been shown to reversibly antagonise thromboxane A2 (TXA2)-induced contraction of rabbit aortic strips at an optimal concentration of 25 μm in the perfusate. Separately, over a dose range of 50-400 mg/kg/p.o., TXA2 production was inhibited between 39% and 85% in spontaneously clotted rabbit blood. In addition, we have shown that TXA2 formation following arachidonic acid-induced aggregation of platelet-rich plasma (PRP) is similarly inhibited. Ditazole however did not inhibit prostacyclin (PGI2) production in rabbit aortic rings following oral drug administration over a dose range of 50-400 mg/kg. At 1000 and 2000 mg/kg PGI2 production was inhibited by 23% and 41% respectively. TXA2 and PGI2 levels were measured by radioimmunoassay of their stable derivatives TXB2 and 6-keto-PGF1α. It is suggested that the mode of action of ditazole may be more specific than the cyclo-oxygenase/PG-synthetase blocking activity of most other non-steroidal anti-inflammatory drugs.

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