CYCLOOXYGENASE INDIPENDENT PLATELET AGGREGATION:RELATION WITH ASPI RIN CONCENTRATION

Low doses of aspirin (20 mg/day) were previously reported to be uneffective in preventing platelet aggregation (PA) induced by pairs of aggregating agents such as PAF and adrenalin.This was in part attributed to the inability of such treatment to inhibit lipo oxygenase-dependent PA.The latter can be observed in vitro in"aspl rinated"platelets stimulated with high quantities of aggregating -agents.The aim of this study was to evaluate if the lipooxygenase-dependent PA was influenced by aspirin in a dose-dependent fashion. PA was studied in platelet rich plasma (PRP)(Born's method) by using threshold doses of aggregating agents (TDA) such as PAF(4-75 nM),epinephrine(0.6-2 μM) and collagen(2-4 μg/ml).PA performed in PRP pretrated with 100μM aspirin was fully prevented;in the same samples thromboxane (Tx) A2 evaluated by its metabolite Tx B2 was almost absent.Increasing amount of PAF(20 fold TDA),epinephrine(20 fold TDA) and collagen (36 fold TDA) do aggregate"aspirinated"pla telets;similarly"aspirinated"platelets aggregate when stimulated-with a pair of aggregating agents (TDA of PAF+epinephrine).This phenomenon was not detected if platelets were incubated with higher amounts of aspirin (250-500 μM).The study suggests that aspirin could influence lipooxygenase-dependent PA.This hypothesis is sup ported by a research showing the aspirin inhibits dose-dependently platelet HETE formation.A further study is now in progress to eva luate the influence of high doses of aspirin on cyclooxygenase-i"n dependent PA in vivo.

The effect of chlorin e6 drug on platelet aggregation activity

Biomedical Photonics ◽

10.24931/2413-9432-2019-8-3-4-10 ◽

2019 ◽

Vol 8 (3) ◽

pp. 4-10 ◽

Cited By ~ 1

Author(s):

N. N. Petrishchev ◽

M. A. Galkin ◽

T. G. Grishacheva ◽

I. N. Dementjeva ◽

S. G. Chefu

Keyword(s):

Platelet Aggregation ◽

Laser Irradiation ◽

Ex Vivo ◽

Platelet Rich Plasma ◽

Dependent Manner ◽

Functional Changes ◽

Aggregation Activity ◽

The goal of the study is to evaluate the effect of Radachlorin (OOO “RADA-PHARMA”, Russia) (RC) on platelet aggregation in ex vivo and in vivo experiments. The experiments were conducted on male Wistar rats. Platelet aggregation activity was determined in platelet-rich plasma (PRP) using a turbidimetric method and the aggregation inducer was ADP at a final concentration of 1.25 μM. PRP samples containing RC were irradiated with ALOD-Granat laser device (OOO “Alkom Medika”, Russia) at 662 nm wavelength with 0.05 W/cm2 power density. After a 5-minute incubation of PRP with RC in the dark, dose-dependent inhibition of platelet aggregation was observed. Laser irradiation (12.5 J/cm2 and, especially, 25 J/cm2) increased the inhibitory effect of RC. 3 hours after intravenous administration of RC, the rate and intensity of platelets aggregation did not change, while disaggregation slowed down significantly. Irradiation at a dose of 5 J/cm2 did not affect the platelets aggregation kinetics, and disaggregation slowed down even more at 10 J/cm2, and at 20 J/cm2 the rate and intensity of platelets aggregation decreased, and no disaggregation occurred.In vitro, RC inhibited the ADP-induced platelet aggregation in rats in a dose-dependent manner; after laser irradiation, this effect was enhanced significantly. The effect of RC on circulating platelets leads to a change in their functional state, which manifests in slowing down the disaggregation after exposure to ADP. After laser irradiation (10 J/cm2 and, especially, 20 J/cm2), the severity of the functional changes increases. The role of decreasing the disaggregation activity of platelets in the mechanism of vascular thrombosis in the affected area of photodynamic therapy (PDT) is discussed.

MECHANISMS FOR THE IN VIVO ANTIPLATELET EFFECTS OF ORGANIC NITRATES

10.1055/s-0038-1643435 ◽

1987 ◽

Author(s):

R De Caterina ◽

D Giannessi ◽

W Bernini ◽

A Mazzone

Keyword(s):

Platelet Aggregation ◽

Platelet Function ◽

Isosorbide Dinitrate ◽

Platelet Rich Plasma ◽

Secondary Wave ◽

Organic Nitrates ◽

Inhibit Platelet Aggregation ◽

Threshold Doses

Organic nitrates (nitroglycerin, isosorbide dinitrate) are inhibitors of platelet function more effective in vivo than in vitro (Am J Cardiol 1984; 53:1683), the in vivo effect requiring concentrations 10-100 times lower than in vitro. We have previously excluded that such difference is due to elicitation by nitrates of prostacyclin synthesis in human endothelial cells or vascular fragments (Circulation 1985; 71:176). In the present study we evaluated alternative explanations: that the difference is due (1) to generation of more active drug metabolites; (2) to synergism between nitrates and prostacyclin in the inhibition of platelet function. Isosorbide dinitrate (ISDN) and its two main in vivo metabolites, isosorbide-2-mononitrate (IS-2-MN) and isosorbide-5-mononitrate (IS-5-MN), were compared in their ability to inhibit platelet aggregation and thromboxane (TX) B2 formation (RIA) in respone to threshold doses of ADP, adrenaline, collagen, arachidonic acid and thrombin in citrated platelet-rich plasma. The same tests were performed in 10 healthy volunteers before, during (at 5, 15 and 30 min) and after infusion of the three drugs at 8 mg/h for 30 min in 3 different days. Finally, the concentration of prostacyclin (and its stable analogue Iloprost) added in vitro to platelets, and required to inhibit platelet aggregation by 50% (IC50) after 5 min pre-incubation of platelets with nitrates was determined. In vitro incubation of platelets with IS-2-MN resulted in greater inhibition of both aggregation and TX formation (by ADP and adrenaline) than with ISDN and IS-5-MN. At 10−7M, only IS-2-MN significantly inhibited aggregation (−12%, P< 0.05) and TX formation (from 9.2±1.8 to 5.9± 0.6 ng/ml) by ADP, while minimum effective concentrations were 10−7M for ISDN and 10−7m for IS-5-MN. These in vitro differences are unlikely to be the explanation of in vivo findings, since IS-2-MN, ISDN and IS-5-MN were equipotent when administered in vivo (complete abolition of secondary wave after ADP and adrenaline at 30 min of infusion). At supra-threshold doses of all the aggregating agents, all three drugs, at 10−7M, decreased IC50 for prostacyclin from 2.9± 1.3 to 0.32± 0.18 nM (P< 0.01). Synergim with prostacyclin is most likely to account, at least partially, for in vivo antiplatelet effects by organic nitrates.

Enhancement of ADP-induced Platelet Aggregation by Adrenaline in Vivo and Its Prevention

10.1055/s-0038-1647788 ◽

1973 ◽

Vol 29 (02) ◽

pp. 490-498 ◽

Cited By ~ 6

Author(s):

Hiroh Yamazaki ◽

Itsuro Kobayashi ◽

Tadahiro Sano ◽

Takio Shimamoto

Keyword(s):

Platelet Count ◽

Platelet Aggregation ◽

Platelet Rich Plasma ◽

The Other ◽

Endothelial Surface ◽

Important Interaction ◽

Blood Coagulability ◽

The Difference

SummaryThe authors previously reported a transient decrease in adhesive platelet count and an enhancement of blood coagulability after administration of a small amount of adrenaline (0.1-1 µg per Kg, i. v.) in man and rabbit. In such circumstances, the sensitivity of platelets to aggregation induced by ADP was studied by an optical density method. Five minutes after i. v. injection of 1 µg per Kg of adrenaline in 10 rabbits, intensity of platelet aggregation increased to 115.1 ± 4.9% (mean ± S. E.) by 10∼5 molar, 121.8 ± 7.8% by 3 × 10-6 molar and 129.4 ± 12.8% of the value before the injection by 10”6 molar ADP. The difference was statistically significant (P<0.01-0.05). The above change was not observed in each group of rabbits injected with saline, 1 µg per Kg of 1-noradrenaline or 0.1 and 10 µg per Kg of adrenaline. Also, it was prevented by oral administration of 10 mg per Kg of phenoxybenzamine or propranolol or aspirin or pyridinolcarbamate 3 hours before the challenge. On the other hand, the enhancement of ADP-induced platelet aggregation was not observed in vitro, when 10-5 or 3 × 10-6 molar and 129.4 ± 12.8% of the value before 10∼6 molar ADP was added to citrated platelet rich plasma (CPRP) of rabbit after incubation at 37°C for 30 second with 0.01, 0.1, 1, 10 or 100 µg per ml of adrenaline or noradrenaline. These results suggest an important interaction between endothelial surface and platelets in connection with the enhancement of ADP-induced platelet aggregation by adrenaline in vivo.

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

10.1055/s-0038-1649080 ◽

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.

Soluble Thrombomodulin Purified from Human Urine Exhibits a Potent Anticoagulant Effect In Vitro and In Vivo

10.1055/s-0038-1653872 ◽

1995 ◽

Vol 73 (05) ◽

pp. 805-811 ◽

Cited By ~ 12

Author(s):

Yasuo Takahashi ◽

Yoshitaka Hosaka ◽

Hiromi Niina ◽

Katsuaki Nagasawa ◽

Masaaki Naotsuka ◽

...

Keyword(s):

Human Urine ◽

Specific Activity ◽

Anticoagulant Activity ◽

Rabbit Lung ◽

Soluble Thrombomodulin ◽

Molecular Weights ◽

Dose Dependent Fashion ◽

SummaryWe examined the anticoagulant activity of two major molecules of soluble thrombomodulin purified from human urine. The apparent molecular weights of these urinary thrombomodulins (UTMs) were 72,000 and 79,000, respectively. Both UTMs showed more potent cofactor activity for protein C activation [specific activity >5,000 thrombomodulin units (TMU)/mg] than human placental thrombomodulin (2,180 TMU/mg) and rabbit lung thrombomodulin (1,980 TMU/mg). The UTMs prolonged thrombin-induced fibrinogen clotting time (>1 TMU/ml), APTT (>5 TMU/ml), TT (>5 TMU/ml) and PT (>40 TMU/ml) in a dose-dependent fashion. These effects appeared in the concentration range of soluble thrombomodulins present in human plasma and urine. In the rat DIC model induced by thromboplastin, administration of UTMs by infusion (300-3,000 TMU/kg) restored the hematological abnormalities derived from DIC in a dose-dependent fashion. These results demonstrate that UTMs exhibit potent anticoagulant and antithrombotic activities, and could play a physiologically important role in microcirculation.

Decreased Platelet Vitamin C in Diabetes Mellitus; Possible Role in Peraggregatoon

10.1055/s-0039-1687640 ◽

1979 ◽

Author(s):

K.E. Sarji ◽

J. Gonzalez ◽

H. Hempling ◽

J.A. Colwell

Keyword(s):

Ascorbic Acid ◽

Arachidonic Acid ◽

Platelet Aggregation ◽

Vitamin C ◽

Platelet Rich Plasma ◽

Solution Ph ◽

Dose Dependent Fashion ◽

Insulin Dependent Diabetic ◽

Induced Aggregation

To determine whether Vitamin C might relate to the increased platelet sensitivity in the diabetic, we have measured levels of platelet Vitamin C and studied the effects of Vitamin C on platelet aggregation. Ascorbic acid levels in washed platelets from diabetics were significantly lower than from normals (4s.2±3 μg/1010 platelets vs. 2s.s±2 μg/1010 platelets, p<.001). The effects of ascorbic acid on platelet aggregation in vitro were studied by adding ascorbic acid in buffered solution (pH 7.35) prior to-aggregating agents. Ascorbic acid in platelet-rich plasma consistently inhibited platelet aggregation with threshold concentrations of ADP, epinephrine, and collagen. With washed platelets, ascorbic acid inhibited arachidonic, acid-induced aggregation. When platelets were incubated at 37°C for 10 minutes with varying concentrations of ascorbic acid, rewashed, and aggregation with arachidonic acid tested, aggregation was inhibited in a linear dose-dependent fashion. Oral ingestion of ascorbic acid (2 gm/day) for seven days by normal non-smoking males produced a marked inhibition of aggregation. In a similar study, platelets from an insulin-dependent diabetic showed no change in aggregation. These results suggest that platelet levels of ascorbic acid may relate to the hyperaggregat ion of platelets from diabetics.

Are Platelet Aggregation Tests the Best Way to Assess New Drugs for Arterial Disease

General medicine and Clinical Practice ◽

10.31579/2639-4162/003 ◽

2018 ◽

Vol 1 (1) ◽

pp. 01-03

Author(s):

Mark I. M. Noble

Keyword(s):

Platelet Aggregation ◽

Platelet Function ◽

Platelet Rich Plasma ◽

New Drugs ◽

In Vitro Test ◽

In Vivo Efficacy ◽

Experimental Animals ◽

Stenosed Artery

Over many years, laboratory testing of platelet aggregability have been carried out in attempts to develop drugs that would prevent thrombosis in arteries. The problems encountered included the question of methodology. Blood samples have to be anticoagulated in order to study the platelets. Anti-coagulation with citrate and tests on derived platelet rich plasma did not correlate at all well with thrombus growth in the stenosed coronary arteries of experimental animals and citrate removes the calcium ions which are vital for platelet function. Anticoagulation with heparin also interfered with platelet function, so that now, hirudins are the preferred anticoagulant. However it was observed that if, instead of stimulating platelet aggregation with adrenaline or ADP, serotonin was applied to the preparation, very little aggregation took place in spite of serotonin 5HT2A antagonists being the most potent inhibitors of thrombus growth in experimental animals. Another indicator that primary platelet agggregation is not a predictor of in vivo efficacy was the finding that 5HT2A antagonism inhibited aggregate growth. In a stenosed artery the platelets are activated by increased shear stress and blood turbulence with release of platelet serotonin causing positive feedback activation of more platelets. At present, there does not seem to be a bench in vitro test that accurately predicts in vivo efficacy in stenosed artery occlusive thrombosis.

Arginine vasopressin release from human platelets after irreversible aggregation

Clinical Science ◽

10.1042/cs0780113 ◽

1990 ◽

Vol 78 (1) ◽

pp. 113-116 ◽

Cited By ~ 7

Author(s):

Giovanni Anfossi ◽

Elena Mularoni ◽

Mariella Trovati ◽

Paola Massucco ◽

Luigi Mattiello ◽

...

Keyword(s):

Platelet Aggregation ◽

Arginine Vasopressin ◽

Platelet Rich Plasma ◽

Human Platelets ◽

Vasopressin Release ◽

Irreversible Aggregation ◽

Local Release

1. The release of arginine vasopressin from human platelets was investigated in platelet-rich plasma after irreversible aggregation induced by adenosine 5′-pyrophosphate, collagen, sodium arachidonate, thrombin and adrenaline in vitro. 2. Arginine vasopressin levels were significantly higher in the supernatant from stimulated platelet-rich plasma than from unstimulated samples, reaching 3.5 × 10−12 (range 1.6–12.5 × 10−12) mol/l in the absence of an aggregating agent, 8.8 × 10−12 (range 4.2–17.5 × 10−12) mol/l after adenosine 5′-pyrophosphate, 13.7 × 10−12 (2.2–63.2 × 10−12) mol/l after collagen, 7.8 × 10−12 (2.2–14.6 × 10−12) mol/l after sodium arachidonate, 7.8 × 10−12 (2.2–16.3 × 10−12) mol/l after thrombin and 12.2 × 10−12 (4.8–32.1 × 10−12) mol/l after adrenaline. 3. An arginine vasopressin level of 18 × 10−12 mol/l, which can be achieved physiologically, increased the sensitivity of platelets to adenosine 5′-pyrophosphate and collagen in vitro; the same concentration of arginine vasopressin caused a potentiation of the effect of catecholamines on the response of platelets to sodium arachidonate. 4. These results indicate that intraplatelet arginine vasopressin is released during aggregation and suggest that a local release of arginine vasopressin could occur after complete platelet aggregation in vivo.

Endotoxin-Induced Platelet Activation in Human Whole Blood In Vitro

10.1055/s-0038-1647499 ◽

1988 ◽

Vol 59 (03) ◽

pp. 378-382 ◽

Cited By ~ 11

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 ◽

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.

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

10.1055/s-0039-1689380 ◽

1975 ◽

Cited By ~ 1

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.