The Effect of Endotoxins on Generation of Thrombin in the Platelet Atmosphere

1975 ◽  
Author(s):  
J. Vermylen ◽  
D. Fumarola ◽  
N. Semeraro
Keyword(s):  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Gradient Centrifugation ◽  
Human Platelets ◽  
Serotonin Release ◽  
Bacterial Endotoxins ◽  
Normal Human ◽  
Bacterial Lipopolysaccharides ◽  
Vitro Effect

Human platelets, washed by repeated albumin density gradient centrifugation, aggregate strongly, occasionally in 2 waves, 3 to 5 minutes after addition of both calcium ions (2.10−3 M f.c.) and one tenth volume normal human serum, provided the serum contains at least 0.6% residual prothrombin. This aggregation is prevented by heparin or hirudin. Samples removed at the onset of aggregation rapidly clot purified fibrinogen, whereas the serum-CaCl2 mixture alone does not clot purified fibrinogen within 24 hours. It is therefore concluded that thrombin is rapidly generated in the platelet atmosphere.The in vitro effect of endotoxins on human, in contrast to rabbit, platelets is not well established. Using eight different bacterial lipopolysaccharides we failed to demonstrate aggregation in human platelet-rich plasma or of washed platelets or to find significant 14C-serotonin release. On the other hand, all these endotoxins in a final concentration of 100 μg/ml consistently shortened the latent period before aggregation in the washed platelets-serum-CaCl2 system. It is concluded that bacterial endotoxins enhance the generation of thrombin in the atmosphere of 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.

Effect of Lidoflazine (R 7904) on Human Platelet Function in Vitro

1972 ◽  
Vol 28 (02) ◽  
pp. 228-236 ◽  
Author(s):  
F De Clerck
Keyword(s):  
Platelet Function ◽  
Mode Of Action ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Serotonin Release ◽  
Clot Retraction ◽  
Plasma Coagulation ◽  
Release Reaction ◽  
Platelet Release

SummaryThe effect of lidoflazine and of cinnarizine on human platelet function in vitro was compared to that of dipyridamole.Pre-incubation for 30 min at 37° C of platelet rich plasma with lidoflazine or with dipyridamole 5 ×10–4 M resulted in an appreciable inhibition of collagen aggregation in particular and to a lesser extent of ADP aggregation; cinnarizine was marginally active only.Clot retraction was inhibited by lidoflazine and by dipyridamole. Experiments on biphasic ADP aggregation and C14-serotonin release during aggregation show that lidoflazine reduces the platelet release reaction.The possible mode of action of the compound is discussed.Plasma coagulation and PF – 3 availability were not affected.

Effects of Lead Acetate on Platelet Aggregation, Ultrastructure and Serotonin Release

1971 ◽  
Vol 26 (03) ◽  
pp. 455-466 ◽  
Author(s):  
R. B Davis ◽  
G. C Holtz
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Lead Acetate ◽  
Platelet Rich Plasma ◽  
Adenosine Diphosphate ◽  
Blood Platelet ◽  
Human Platelets ◽  
Serotonin Release ◽  
Aggregation Of Platelets

SummaryThe effects of lead on blood platelet function and ultrastructure have been investigated. Lead acetate was injected intravenously in 27 rats and was added to rat and human platelet rich plasma in vitro. In vitro studies showed that concentrations of 2.5 × 10-3 M lead acetate reduced or blocked aggregation of rat and human platelets by adenosine diphosphate, collagen, and thrombin. Radioactive serotonin release from human platelets was inhibited by 10-4 M lead acetate. One hour after the injection of lead, platelet aggregation by thrombin was reduced, but platelet aggregation by adenosine diphosphate and collagen showed little change. Three days after lead, aggregation of platelets by collagen and thrombin was blocked and aggregation by adenosine diphosphate reduced. Thrombocytopenia was present 4 days after intravenous lead acetate. Electron micrographs of platelets showed that the mean number of mitochondria per platelet was increased, whereas alpha granules were reduced. Dense bodies were not significantly changed. Lead acetate affects platelet function in concentrations reported in human bone marrow in lead poisoning, and may relate to the binding of free sulfhydryl groups by lead.

Studies on in vitro effect of picotamide on human platelet aggregation in platelet-rich plasma and whole blood

1995 ◽  
Vol 77 (5) ◽  
pp. 399-410 ◽  
Author(s):  
Giovanni Anfossi ◽  
Simona Parisi ◽  
Isabella Russo ◽  
Elena M. Mularoni ◽  
Paola Massucco ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Human Platelet Aggregation ◽  
Vitro Effect

Impairment of Human Platelet Aggregation and Serotonin Release Caused in Vitro by Echis Colorata Venom

1973 ◽  
Vol 30 (01) ◽  
pp. 191-198 ◽  
Author(s):  
Haim Biran ◽  
Alexander Dvilansky ◽  
Ilana Nathan ◽  
Avinoam Livne
Keyword(s):  
Platelet Aggregation ◽  
Functional Impairment ◽  
Human Platelet ◽  
Human Platelets ◽  
Endothelial Damage ◽  
Serotonin Release ◽  
Bleeding Tendency ◽  
Human Platelet Aggregation

SummaryAggregation of washed human platelets, induced by either ADP, thrombin or collagen, was decreased by Echis colorata venom (EVC). With ADP as an inducer, the inhibition of aggregation was proportional to the venom concentration, starting from 0.27 μg/ml and attaining full inhibition with venom concentration of 9 μg/ml. Higher concentrations were required for comparable venom effects when collagen or thrombin were used as inducers. Based on serotonin release measurements and platelet counting, it is concluded that the ECV-diminished aggregation is not due to platelet lysis. Thrombin-dependent serotonin release was inhibited by the venom to an extent proportional to the log ECV concentration at a range of 0.27 to 90 μg/ml. ECV effeces on serotonin release are apparently independent on its effects on aggregation, since similar results were obtained either with or without EDTA.Endothelial damage and defibrination are already known to be associated with the bleeding tendency caused by ECV. The present data disclose a functional impairment of platelets as an additional antihemostatic effect of this venom.

scholarly journals 3’5’-Adenosine Diphosphate (3′5′ADP):A Physiological Inhibitor of Platelet Aggregation and Platelet Release Reaction

1977 ◽  
Author(s):  
K. Subbarao ◽  
K. Jaya
Keyword(s):  
Platelet Aggregation ◽  
Coenzyme A ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Serotonin Release ◽  
Dependent Manner ◽  
Release Reaction ◽  
Inhibition Of Platelet Aggregation ◽  
Vitro Effect ◽  
Aggregation Of Platelets

Certain analogues of adenosine have been shown to inhibit ADP-induced platelet aggregation. We therefore studied the in vitro effect of 3′5′ADP and coenzyme A on human platelet aggregation and [14C]-serotonin release reaction induced by the addition of ADP, thrombin, collagen and epinephrine to human platelet rich plasma (PRP). It was found that coenzyme A Li3·2H2O at a concentration of 0.12 mM strongly inhibited ADP-induced platelet aggregation of PRP but did not show similar effect on the aggregation of platelets induced by other aggregating agents. The 3′5′ADP which is a part of coenzyme A structure, on the other hand, inhibited both ADP and thrombin induced platelet aggregation. The extent of inhibition of platelet aggregation by coenzyme A and 3′5′ADP was found to depend upon the concentration of the inhibitor and the incubation time. Whereas 3′5′ADP Li2·3H2O at a concentration of 10 μM produced about 70% inhibition of ADP-induced platelet aggregation of human PRP, total inhibition of thrombin induced platelet aggregation was observed when platelets were incubated with 60 μM of 3′5′ADP. The 3′5′ADP also inhibited the [14C]-adeonsine uptake by platelets in a concentration dependent manner. The inhibitory potency of 3′5′ADP on platelet aggregation was found to be 10-fold higher than that of N6-2′-0-dibutyryl-cyclic 3′5′-adenosine monophosphate. The inhibition of platelet aggregation by coenzyme A and 3′5′ADP was always accompanied by the inhibition of [14C]-serotonin release reaction. If coenzyme A and 3′5′ADP are indeed physiological inhibitors of platelet aggregation, then aggregation of platelets should depend on metabolic events that regulate the concentration of these agents in blood.

scholarly journals Inhibitory Effect of Diamines and Polyamines on Human Platelet Aggregation and [14C]-Serotonin Release Reaction

1977 ◽  
Author(s):  
K. Subbarao ◽  
F. Forestier
Keyword(s):  
Platelet Function ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Inhibitory Effect ◽  
Serotonin Release ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Release Reaction ◽  
Aggregation Of Platelets

Physiological diamines and polyamines occur in high concentrations in various parts of animal tissues. These amines are known to interact with and stabilize nucleic acids, membranes and ribosomes (Tabor and Tabor, Pharmac. Rev., 16, 245). The effect of putrescine, cadaverine, spermidine and spermine on platelet function is not yet fully explored. We studied the effect of these reagents on in vitro aggregation of human platelet rich plasma (PRP) induced by the addition of ADP, thrombin, collagen and serotonin. Cadaverine, spermidine and spermine at concentrations from 2-5 μM strongly inhibited the aggregation of platelets and the [14C]-serotonin release reaction induced by ADP and thrombin in a concentration dependent manner, but did not show any effect on aggregation induced by other agents. Putrescine, on the other hand, failed to produce any effect on the aggregation of platelets and [14C]-serotonin release reaction. Studies on the binding of purified human thrombin treated with [14C]-diisopropylfluoro-phosphate (DFP) to washed human platelets indicated that cadaverine (1-5 μmoles) increased the binding of total [14C]-DFP-thrombin to platelets by 30%. The data suggest that the alteration of platelet function by diamines and polyamines was probably achieved by their binding to platelet membranes.

Immune Injury to Human Platelets Mediated By IgG Fc Receptor is Prevented by Prostacyclin

1979 ◽  
Author(s):  
J. Hawiger ◽  
S.K. Parkinson ◽  
S. Timmons ◽  
A.D. Glick
Keyword(s):  
Human Platelet ◽  
Protein A ◽  
Active Agent ◽  
Human Platelets ◽  
Fc Receptor ◽  
Serotonin Release ◽  
Fc Fragment ◽  
Immune Injury ◽  
Dose Dependent

Immune injury to human platelets by drugs, bacteria, and viruses which form antigenantibody complexes is mediated by the IgG Fc receptor on human platelets and results in thrombocytopenia. We studied whether immune injury to human platelets mediated by the IgG Fc receptor can be prevented by prostacyclin (Prostagland in 12, PGI2), a novel prost glandin generated by the blood vessel wall. Immune injury to human platelets in whole plasma was elicited by Protein A-bearing staphylococci. Protein A induces binding of I to the human platelet Fc receptor, which results in platelet aggregation and 3H-seroton release in whole plasma. Excess of isolated Fc fragment inhibits aggregation and serotonin release in this model of immune injury. Synthetic PGI2 protected human platelets from this IgG Fc fragment-mediated immune injury in whole plasma. Inhibition was prompt (1 to 5 min) and dose dependent, reaching maximum at 10-6M of PGI2. Removal of plasma proteins and use of IgG-coated cells did not change the inhibitory potency of PGI2, which was at least 1000-fold more active than 6-keto PGF1α. Electron microscopy revealed than PGI2 prevented binding of IgG- coated cel is to human platelet membrane. From comparison with anti-inflammatory steroids (methylprednisolone) and nonsteroidal prostaglandin synthetase inhibitors (ASA), it appears that prostacyclin is the most active agent known the date to protect human platelets from IgG Fc receptor-mediated immune injury in vitro.

scholarly journals Effects of acetyl glyceryl ether phosphorylcholine on human platelet function in vitro

Blood ◽  
1981 ◽  
Vol 58 (5) ◽  
pp. 1027-1031 ◽  
Author(s):  
AJ Marcus ◽  
LB Safier ◽  
HL Ullman ◽  
KT Wong ◽  
MJ Broekman ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Initial Phase ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Strong Stimulus ◽  
Adp Release ◽  
Irreversible Aggregation ◽  
Induced Aggregation

Abstract AGEPC (PAF), at 1.9 x 10(-8) M or higher, induced concentration- dependent aggregation and release in human platelet-rich plasma. Comparative studies with arachidonate, collagen, ionophore, and ADP suggested that AGEPC was a strong stimulus for platelet aggregation and probably a moderate agonist for release, as well as a relatively weak inducer of TXA2 production. The initial phase of AGEPC-induced aggregation was independent of ADP release and TXA2 formation, since it was not inhibited by ASA, apyrase, or CP/CPK. Whereas irreversible aggregation always required ADP release, TXA2 formation was not essential in each instance. Thus, in several experiments, full aggregation responses took place in AGEPC-stimulated platelets that had been pretreated with ASA. AGEPC-induced release of 5-HT, beta - thromboglobulin and PF-4 occurred in parallel and were inhibited by both apyrase and ASA. Washed human platelets did not respond to exogenous AGEPC in the absence of ADP and did not appear to generate significant quantities of AGEPC upon stimulation with thrombin or ionophore.

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

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