Inhibition Of Platelet Aggregation, Malonyldialdehyde And Thromboxane Formation By Hydroperoxides Of Arachidonic Acid

1981 ◽  
Author(s):  
D Aharonv ◽  
J B Smith ◽  
M J Silver
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Lipoxygenase Pathway ◽  
Dose Dependent Fashion ◽  
Induced Aggregation ◽  
Layer Chromatography ◽  
Dose Dependent ◽  
Thromboxane Formation

The arachidonate hydroperoxides 12-HPETE and 15-HPETE were biosynthesized from arachidonic acid using partially purified human platelet lipoxygenase or soybean lipoxidase respectively, and isolated by thin layer chromatography. Both compounds inhibited the arachidonic acid- induced aggregation of washed human platelets, suspended in calcium-free Krebs Henseleit solution, in a dose dependent fashion at concentrations between 1 and 50 uM. No inhibition was seen with up to 100 uM of these hydroperoxides when platelet -rich plasma was used. 12-HPETE (in micromolar concentrations) inhibited the formation of both thromboxane B2 (radioimmunoassay) and malonyldialdehyde (spectrophotometrie assay) when washed platelets were incubated with arachidonic acid. The 12-hydroxide, 12-HETE also inhibited platelet aggregation and thromboxane formation, but was less potent than 12-HPETE. We suggest that arachidonate hydroperoxide generated in platelets via the lipoxygenase pathway modulates platelet aggregation induced by arachidonic acid by inhibiting thromboxane formation.

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

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.

scholarly journals Preclinical studies of RUC-4, a novel platelet αIIbβ3 antagonist, in non-human primates and with human platelets

2019 ◽  
Vol 3 (2-3) ◽  
pp. 65-74 ◽  
Author(s):  
Spandana Vootukuri ◽  
Jihong Li ◽  
Mark Nedelman ◽  
Craig Thomas ◽  
Jiang-Kang Jiang ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Initial Slope ◽  
Receptor Blockade ◽  
St Segment Elevation ◽  
St Segment ◽  
Aggregation Inhibition ◽  
Induced Aggregation ◽  
Dose Dependent

AbstractIntroduction:We are developing the novel αIIbβ3 antagonist, RUC-4, for subcutaneously (SC)-administered first-point-of-medical-contact treatment for ST segment elevation myocardial infarction (STEMI).Methods:We studied the (1) pharmacokinetics (PK) of RUC-4 at 1.0, 1.93, and 3.86 mg/kg intravenous (IV), intramuscular (IM), and SC in non-human primates (NHPs); (2) impact of aspirin on RUC-4 IC50in human platelet-rich plasma (PRP); (3) effect of different anticoagulants on the RUC-4 IC50in human PRP; and (4) relationship between αIIbβ3 receptor blockade by RUC-4 and inhibition of ADP-induced platelet aggregation.Results:(1) All doses of RUC-4 were well tolerated, but animals demonstrated variable temporary bruising. IM and SC RUC-4 reached dose-dependent peak levels within 5–15 minutes, with T1/2s between 0.28 and 0.56 hours. Platelet aggregation studies in NHPs receiving IM RUC-4 demonstrated >80% inhibition of the initial slope of ADP-induced aggregation with all three doses 30 minutes post-dosing, with subsequent dose-dependent loss of inhibition over 4–5 hours. (2) The RUC-4 IC50for ADP-induced platelet aggregation was unaffected by aspirin treatment (40±9 nM vs 37±5 nM;p= 0.39). (3) The RUC-4 IC50was significantly higher in PRP prepared from D-phenylalanyl-prolyl-arginyl chloromethyl ketone (PPACK)-anticoagulated blood compared to citrate-anticoagulated blood using either thrombin receptor activating peptide (TRAP) (122±17 vs 66±25 nM;p= 0.05;n= 4) or ADP (102±22 vs 54±13;p<0.001;n= 5). (4) There was a close correspondence between receptor blockade and inhibition of ADP-induced platelet aggregation, with aggregation inhibition beginning with ~40% receptor blockade and becoming nearly complete at >80% receptor blockade.Discussion:Based on these results and others, RUC-4 has now progressed to formal preclinical toxicology studies.

Effects of Methylprednisolone and Hydrocortisone on Aggregation of Rabbit Platelets Induced by Arachidonic Acid and Other Aggregating Substances

1981 ◽  
Vol 46 (04) ◽  
pp. 676-679 ◽  
Author(s):  
Frank Glass ◽  
Howard Lippton ◽  
Philip J Kadowitz
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Adenosine Diphosphate ◽  
Actual Mechanism ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition ◽  
The Difference ◽  
Induced Aggregation ◽  
Dose Dependent

SummaryThe effects of methylprednisolone and hydrocortisone on platelet aggregation induced by arachidonic acid (AA), collagen, adenosine diphosphate (ADP), prostaglandin (PG) H2, and a stable PGH2 analog, were studied in platelet-rich plasma (PRP) from the rabbit. Incubation of either steroid in PRP inhibited AA-, collagen- and ADP-induced platelet aggregation in a concentration-related manner. The dose of methylprednisolone required to inhibit 0.02 mM AA-induced aggregation was lower than that required to inhibit either 0.08 μg/ml collagen or 0.2 μM ADP-induced aggregation. Methylprednisolone produced a dose dependent inhibition of platelet aggregation induced by PGH2 and the stable PGH2 analog. In washed platelets methylprednisolone was more effective in inhibiting AA-induced aggregation than ADP- or collagen-induced aggregation; however, the difference in effect was less than in PRP. Platelet responses to AA in PRP from rabbits treated with hydrocortisone or methylprednisolone, 100 mg/kg i.v., were inhibited in a transient manner, whereas aggregation induced by ADP under similar conditions was unchanged. Since inhibition of aggregation elicited by AA occurred at concentrations which do not influence PGH2-, PGH2 analog-, collagen- or ADP-induced aggregation, the present data suggest that the steroids may inhibit the incorporation, the release, or the metabolism of arachidonic acid in platelets. The actual mechanism of this relatively specific inhibition of AA-induced aggregation by anti-inflammatory steroids is uncertain but may be related to the membrane “stabilizing” properties of methylprednisolone and hydrocortisone.

The Effect of Red Blood Cells on the ADP-induced Aggregation of Human Platelets in Flow Through Tubes

1990 ◽  
Vol 63 (01) ◽  
pp. 112-121 ◽  
Author(s):  
David N Bell ◽  
Samira Spain ◽  
Harry L Goldsmith
Keyword(s):  
Platelet Aggregation ◽  
Shear Rate ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Platelet Rich Plasma ◽  
Mean Transit Time ◽  
White Blood Cells ◽  
Aggregate Size ◽  
Human Platelets ◽  
Induced Aggregation

SummaryThe effect of red blood cells, rbc, and shear rate on the ADPinduced aggregation of platelets in whole blood, WB, flowing through polyethylene tubing was studied using a previously described technique (1). Effluent WB was collected into 0.5% glutaraldehyde and the red blood cells removed by centrifugation through Percoll. At 23°C the rate of single platelet aggregtion was upt to 9× greater in WB than previously found in platelet-rich plasma (2) at mean tube shear rates Ḡ = 41.9,335, and 1,920 s−1, and at both 0.2 and 1.0 µM ADP. At 0.2 pM ADP, the rate of aggregation was greatest at Ḡ = 41.9 s−1 over the first 1.7 s mean transit time through the flow tube, t, but decreased steadily with time. At Ḡ ≥335 s−1 the rate of aggregation increased between t = 1.7 and 8.6 s; however, aggregate size decreased with increasing shear rate. At 1.0 µM ADP, the initial rate of single platelet aggregation was still highest at Ḡ = 41.9 s1 where large aggregates up to several millimeters in diameter containing rbc formed by t = 43 s. At this ADP concentration, aggregate size was still limited at Ḡ ≥335 s−1 but the rate of single platelet aggregation was markedly greater than at 0.2 pM ADP. By t = 43 s, no single platelets remained and rbc were not incorporated into aggregates. Although aggregate size increased slowly, large aggregates eventually formed. White blood cells were not significantly incorporated into aggregates at any shear rate or ADP concentration. Since the present technique did not induce platelet thromboxane A2 formation or cause cell lysis, these experiments provide evidence for a purely mechanical effect of rbc in augmenting platelet aggregation in WB.

Testosterone Potentiation of Ionophore and ADP Induced Platelet Aggregation : Relationship to Arachidonic Acid Metabolism

1981 ◽  
Vol 46 (02) ◽  
pp. 538-542 ◽  
Author(s):  
R Pilo ◽  
D Aharony ◽  
A Raz
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Unsaturated Fatty Acids ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Arachidonic Acid Metabolism ◽  
Ionophore A23187 ◽  
Low Concentrations ◽  
Induced Aggregation

SummaryThe role of arachidonic acid oxygenated products in human platelet aggregation induced by the ionophore A23187 was investigated. The ionophore produced an increased release of both saturated and unsaturated fatty acids and a concomitant increased formation of TxA2 and other arachidonate products. TxA2 (and possibly other cyclo oxygenase products) appears to have a significant role in ionophore-induced aggregation only when low concentrations (<1 μM) of the ionophore are employed.Testosterone added to rat or human platelet-rich plasma (PRP) was shown previously to potentiate platelet aggregation induced by ADP, adrenaline, collagen and arachidonic acid (1, 2). We show that testosterone also potentiates ionophore induced aggregation in washed platelets and in PRP. This potentiation was dose and time dependent and resulted from increased lipolysis and concomitant generation of TxA2 and other prostaglandin products. The testosterone potentiating effect was abolished by preincubation of the platelets with indomethacin.

Effects of Ethanol on Pathways of Platelet Aggregation In Vitro

1988 ◽  
Vol 59 (03) ◽  
pp. 383-387 ◽  
Author(s):  
Margaret L Rand ◽  
Marian A Packham ◽  
Raelene L Kinlough-Rathbone ◽  
J Fraser Mustard
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Secondary Phase ◽  
Primary Phase ◽  
Rabbit Platelet ◽  
Membrane Phospholipids ◽  
Rabbit Platelets ◽  
Induced Aggregation

SummaryEthanol, at physiologically tolerable concentrations, did not affect the primary phase of ADP-induced aggregation of human or rabbit platelets, which is not associated with the secretion of granule contents. Potentiation by epinephrine of the primary phase of ADP-induced aggregation of rabbit platelets was also not inhibited by ethanol. However, ethanol did inhibit the secondary phase of ADP-induced aggregation which occurs with human platelets in citrated platelet-rich plasma and is dependent on the formation of thromboxane A2. Inhibition by ethanol of thromboxane production by stimulated platelets is likely due to inhibition of the mobilization of arachidonic acid from membrane phospholipids, as ethanol had little or no effect on aggregation and secretion induced by arachidonic acid or the thromboxane mimetic U46619. Rabbit platelet aggregation and secretion in response to low concentrations of collagen, thrombin, or PAF were inhibited by ethanol. Inhibition of the effects of thrombin and PAF was also observed with aspirin-treated platelets. Thus, in addition to inhibiting the mobilization of arachidonate for thromboxane formation that occurs with most agonists, ethanol can also inhibit aggregation and secretion through other effects on platelet responses.

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 Heparin on Aggregation, Release Reaction and Thromboxane A2synthesis in Human Platelets

1979 ◽  
Author(s):  
H.Y.K. Chuang ◽  
S.F. Mohammad ◽  
R.G. Mason
Keyword(s):  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Thromboxane A2 ◽  
Rabbit Aorta ◽  
Human Platelets ◽  
Appreciable Effect ◽  
Layer Chromatography ◽  
Aggregation Of Platelets ◽  
Platelet Functions

Studies on the effect of heparin on platelet functions have resulted in conflicting observations: heparin has been reported to cause aggregation of platelets, potentiate aggregation induced by various aggregating agents, or cause inhibition of aggregation. Using paritally purified heparin (beef lung or porcine mucosa) we observed that addition of heparin to citrated platelet rich plasma(C-PRP)potentiated the aggregation of platelets induced by ADP, epinephrine, or arachidonic acid. Presence of heparin in C-PRP results in complete inhibition of thrombin induced effects and partial inhibition of platelet aggregation induced by collagen. Presence of heparin in C-PRP also resulted in release of significantly higher concentrations of 14C-serotonin when platelets were challenged by appropriate aggregating agents. Those concentrations of heparin that resulted in potentiation of aggregation had no appreciable effect on c-AiMP or c-GMP levels of platelets. However, the presence of heparin results in a significant elevation of thromboxane A2 as determined by contraction of rabbit aorta or after conversion to thromboxane B2 by thin layer chromatography. These observations are of interest since increased production of thromboxane A2 in the presence of heparin may explain in part, the potentiation of platelet aggregation in vitro or thrombocytopenia observed frequently in patients receiving heparin intravenously Supported in part by grants HL22583 & 20679 from NHLBI of NIH.

scholarly journals Studies on the Biological Effects of Ozone: 10. Release of Factors from Ozonated Human Platelets

1999 ◽  
Vol 8 (4-5) ◽  
pp. 205-209 ◽  
Author(s):  
G. Valacchi ◽  
Velio Bocci
Keyword(s):  
Platelet Aggregation ◽  
Growth Factor ◽  
Transforming Growth Factor ◽  
Platelet Rich Plasma ◽  
Biological Effects ◽  
Transforming Growth Factor Β1 ◽  
Human Platelets ◽  
Dependent Manner ◽  
Dose Dependent ◽  
Tgf Β1

In a previous work we have shown that heparin, in the presence of ozone (O3), promotes a dose-dependent platelet aggregation, while after Ca2+chelation with citrate, platelet aggregation is almost negligible. These results led us to think that aggregation may enhance the release of platelet components. We have here shown that indeed significantly higher amount of platelet-derived growth factor (PDGF), transforming growth factor β1 (TGF-β1) and interleukin-8(IL-8) are released in a dose-dependent manner after ozonation of heparinised platelet-rich plasma samples. These findings may explain the enhanced healing of torpid ulcers in patients with chronic limbischemia treated with O3autohaemoteraphy (O3-AHT).

Comparison of Rapid Platelet Function Assay with Whole Blood Platelet Impedance Aggregometry for the Definition of Aspirin Resistance.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4018-4018
Author(s):  
Anna M. Dyszkiewicz-Korpanty ◽  
Anne Kim ◽  
James D. Burner ◽  
Eugene P. Frenkel ◽  
Ravindra Sarode
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Blood Platelet ◽  
Aspirin Resistance ◽  
Impedance Aggregometry ◽  
Definition Of ◽  
Induced Aggregation

Abstract The reported incidence of aspirin (ASA) resistance ranges from 5 to 30%. Various platelet function assays have been employed to detect aspirin resistance in patients with cardio- and cerebrovascular disease. Such a high proposed incidence of ASA resistance poses a critical need for a rapid point-of -care (POC) platelet function test. Unfortunately, no uniformly accepted definition of ASA resistance exists. Platelet aggregation studies that have been used to define ASA resistance are time consuming and require special technical expertise. The Ultegra Rapid Platelet Function -ASA (RPFA-ASA) has been developed as a POC test that is performed without sample processing. This optical method measures agglutination of fibrinogen-coated beads upon platelet activation with arachidonic acid. In the presence of aspirin effect, however, the agglutination of the beads is inhibited. The described cutoff of ≥ 550 Aspirin Reaction Units (ARU) is termed non-responsiveness to ASA based on a preclinical study and subsequent correlation with epinephrine-induced platelet aggregation in platelet rich plasma. Since RPFA-ASA uses whole blood, we validated its performance characteristics against a classic whole blood platelet aggregation assay (WBA). We studied 50 healthy volunteers, aged 25–75 (24 men, 26 women) with normal CBC, who had not ingested anti-platelet drugs for 14 days prior to the study. Baseline studies included WBA (dual channel aggregometer, Chrono-log Inc., Havertown, PA) using both arachidonic acid (AA -0.5; 0.25 mM) and collagen (1; 2 μg/mL) as well as an RPFA-ASA assay (Accumetrics Inc., San Diego, CA). These studies were repeated after 3 days of ASA (325 mg/d) intake. Based on a review of the literature, we defined an adequate ASA response as a completely inhibited AA-induced platelet aggregation and at least 30% inhibition of collagen-induced aggregation (both concentrations of the agonist). Thus, those with &lt; 30% inhibition of aggregation response to collagen were considered ASA resistant. Eleven subjects were ASA resistant by WBA (20%; 8 females and 3 males (aged 25–63). In contrast, since all 50 subjects achieved ARU values of &lt; 550 ARU, none were recognized as an ASA non-responder by the RPFA-ASA. While the current cutoff of &lt; 550 ARU posed by the Ultegra RPFA-ASA does identify those who have taken ASA, the assay is unable to recognize ASA non-responders. Thus, based on these data, the appropriate cutoff for the recognition of ASA resistance by the RPFA-ASA should be re-adjusted to a significantly lower level to ensure appropriate assay results.

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