Effect of pyridoxal-5'-phosphate on aggregation of platelets from stored human concentrates induced by arachidonic acid

SummaryThe aggregation of platelets collected from maternal/neonatal pairs (n = 240) at the time of childbirth, was studied in response to multiple doses of ADP, collagen, arachidonic acid and ristocetin. Similar responses were obtained from healthy nonpregnant adult controls for comparison. The lag phase, slope of the aggregation curves as well as maximum aggregation (MA%) were recorded and analysed. Neonatal and adult platelets exhibited more enhanced responses to decreasing doses of ADP, arachidonic acid and ristocetin, than maternal platelets. These enhanced responses were exhibited more consistantly in the slopes of the aggregation curves than in MA%. Although neonatal platelets have shown longer lag phase in their responses to collagen, the rate of the aggregation reaction was significantly faster than maternal platelets, with no differences in MA%. These results contradict many previous reports suggesting impaired aggregation responses of neonatal platelets to these agonist. The possible reasons for these contradictions were discussed.

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Specific Desensitization Of Washed Rabbit Platelets By Paf-Acether And Derivatives

10.1055/s-0038-1652802 ◽

1981 ◽

Author(s):

C Lalau Keraly ◽

M Tencé ◽

F Heymans ◽

J Benveniste

Keyword(s):

Arachidonic Acid ◽

Alkyl Chain ◽

Synthetic Analog ◽

Synthetic Compounds ◽

Glycerol Moiety ◽

Rabbit Platelets ◽

Acetyl Group ◽

Induced Aggregation ◽

Aggregation Of Platelets ◽

Very High

PAF-acether-aggregated rabbit platelets did not respond to a second challenge with the same agonist after their spontaneous disaggregation, but still aggregated in the presence of arachidonic acid (AA). When using 1 nM of PAF-acether in the first stimulation, aggregation in response to a second challenge with the same dose was nil. However, when 0.34 nM was used in the first step, aggregation in response to 0.64 nM PAF-acether was 59 96, as compared to control platelets. By contrast, aggregation of platelets pretreated with 1 nM PAF-acether was 72 % in the presence of 2.8 uM AA. Adding fibrinogen (0.34 mg/ml) before the second stimulation did not modify the desensitization pehnom- enon. Supernatants from platelets desensitized with 1 nM PAF- acether exhibited neither aggregating nor inhibitory activity. PAF-acether-induced desensitization could always be overcome, since aspirin-pretreated platelets first stimulated with 10 nM PAF-acether still aggregated with 100 nM of the same agonist, i.e. when using 100 times the amount which induced maximal aggregation. All our experiments were performed in the presence of ADP scavengers and, except for AA-induced aggregation, aspirin. We tested PAF-acether from 4 different cell origins and the semi-synthetic and synthetic compounds. Platelets were cross- desensitized towards PAF-acether from any source. Totally synthetic PAF-acether bearing aC,, alkyl chain at position 1 of the glycerol moiety desensitized platelets as well as the C.g synthetic analog. Lyso-PAF-acether (i.e. a compound lackifig tne acetyl group at the position 2 of the glycerol) (0.5-10.0 nM) and PAF-acether enantiomer (0.5-5.0 nM) neither aggregated nor desensitized platelets to PAF-acether. These results indicate that 1) PAF-acether from any source exhibit at least an identical active molecular site ; 2) the presence and the stereospecific position of the 2-acetyl group are critical for the interaction of PAF-acether with platelets, a result which could indicate the existence of a platelet acceptor (receptor) for PAF-acether. However, these postulated platelet membrane acceptors were never saturated even using very high amounts of the agonist.

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Arachidonic Acid-Induced Aggregation of Platelets from Human Cord Blood Compared with Platelets from Adults

Neonatology ◽

10.1159/000242116 ◽

1985 ◽

Vol 47 (4) ◽

pp. 199-204 ◽

Cited By ~ 14

Author(s):

G. Ahlsten ◽

U. Ewald ◽

T. Tuvemo

Keyword(s):

Arachidonic Acid ◽

Cord Blood ◽

Human Cord Blood ◽

Induced Aggregation ◽

Aggregation Of Platelets

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Platelet Aggregation Induced by a Synthetase-Like Substance and Phospholipase-A.

10.1055/s-0039-1689083 ◽

1975 ◽

Author(s):

S. G. Iatridis ◽

P. G. Iatridis ◽

S. G. Markidou ◽

B. H. Ragatz

Keyword(s):

Arachidonic Acid ◽

Platelet Aggregation ◽

Adenosine Diphosphate ◽

Phospholipase A ◽

Second Phase ◽

Inhibit Platelet Aggregation ◽

Phase Type ◽

Irreversible Aggregation ◽

Cyclic Endoperoxide ◽

Aggregation Of Platelets

Platelets contain arachidonic acid-bearing phospholipids and phospholipase-A (Phl-A); it has been suggested that exposure of these substances to each other by stimuli, such as thrombin or adenosine diphosphate (ADP), would result in liberation of arachidonic acid (AA), which is the precursor of cyclic endoperoxide; a factor causing irreversible aggregation of platelets.By using a saline eluate of a polyurethane (SPU, -polyester elastomer of the thermoplastic type-, secured by exposing saline for two minutes to the inner surface of a polyurethane bag) we observed that platelet (human PRP) aggregation (second phase type, irreversible) could be induced by Phl-A plus SPU or AA plus SPU. These mixtures failed to aggregate aspirinized platelets. Aspirin, however, incubated for 10 minutes with SPU, Phl-A or AA did not inhibit platelet aggregation induced by the addition of the missing factor. In control experiments no aggregation was produced by SPU-saline, saline-Phl-A or saline-AA. SPU plus suboptimal concentrations of ADP or epinephrine induced an immediate in onset aggregation. Phl-A added in reversibly, by ADP, aggregated platelets produced a second phase of aggregation.The results show that AA which is the precursor of cyclic endoperoxide could be liberated by Phl-A. The results also provide evidence that at least two enzymes (synthetase-α and synthetase-β; α is inactive whereas β is active and can be blocked by apsirin) are involved in the process of AA activation and biosynthesis of cyclic endoperoxide.Supported by a grant from the U.S. Public Servie HL-15425.

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Differential Inhibition of Arachidonic Acid Mediated Aggregation of Platelets by Branded and Generic Argatroban Preparations

Blood ◽

10.1182/blood.v116.21.5131.5131 ◽

2010 ◽

Vol 116 (21) ◽

pp. 5131-5131

Author(s):

Christopher Aranda ◽

Debra Hoppensteadt ◽

Omer Iqbal ◽

Bruce E Lewis ◽

Jawed Fareed

Keyword(s):

Arachidonic Acid ◽

Platelet Aggregation ◽

Platelet Activation ◽

Serotonin Release ◽

Final Concentration ◽

Release Mechanism ◽

Clinical Effects ◽

Induced Aggregation ◽

Aggregation Of Platelets ◽

Inhibition Of Thrombin

Abstract Abstract 5131 Argatroban represents a parentral antithrombin agent which is used in the management of anticoagulation in heparin compromised patients. Its main mechanism of action is mediated via inhibition of thrombin and its generation. While its effect on platelet activation inhibition by thrombin have been reported, very little information on the effects of this drug on thromboxane formation and Arachidonic Acid mediated activation of platelets is available. Argatroban and its generic versions namely Slovastan, Argaron and Gartban, may modulate Arachidonic Acid mediated platelet aggregation and release processes. To test this hypothesis a branded version of Argatroban (Mitsubishi – Tanade, Tokyo, Japan) and three generic versions of Argatroban namely Slovastan, Gartban, and Slovastan were compared for their effects on Arachidonic Acid mediated aggregation of platelets in normal healthy male and female volunteers (and n = 4). Other agonists such as Epinephrine, Collagen, and ADP were also used. The effect of Arachidonic Acid on serotonin release was also measured using an Elisa technique for the measurement of serotonin. All of the generic and branded versions of Argatroban produce varying levels of the inhibition of the Arachidonic Acid mediated aggregation of platelets, ranging from the 24 to 36 percent in comparison to the control at a concentration of 1 mg/ mL (p value < 0.05). Interestingly all of the Argatrobans produced a relatively weaker inhibition of the Arachidonic Acid mediated aggregation of platelets 24–26 percent inhibition versus 36 percent at the final concentration of 1 mg/mL. No differences were noted in the aggregation profile of ADP, Collagen, and Epinephrine between the control and the Argatrboban at a final concentration of 1 mg /mL. No differences were noted between the generic and branded Argatroban on all of the other agonists induced aggregation. In the serotonin release assays, all of the generic and branded Argatroban produced a concentration dependent inhibition of serotonin release which was stronger with the branded version of Argatroban. These results indicate that besides the inhibition of thrombin Argatroban is capable of inhibiting platelet activation via other mechanisms. Moreover, the generic versions of Argatroban exhibit a weaker inhibition of Arachidonic Acid mediated platelet aggregation and release. These studies suggest that beside thrombin mediated aggregation Argatroban and its generic versions can modulate platelet activation and release reactions. Furthermore a difference is observed between the generic and branded product which may impact the safety inefficacy profile in these agents. Argatroban is used commonly in the management of patients with heparin induced thrombocytopenia where multiple mechanisms of platelet activation are contributory to the pathogenesis of this syndrome. Modulation of thrombanxane formation and platelet release mechanism by Argatroban may represent an additional mechanism of the clinical effects of this parentral antithrombin agent. Disclosures: No relevant conflicts of interest to declare.

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Detection of Platelet Desensitization in Pregnancy-Induced Hypertension Is Dependent on the Agonist Used

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648174 ◽

1991 ◽

Vol 65 (05) ◽

pp. 474-477 ◽

Cited By ~ 18

Author(s):

Y Ahmed ◽

M H F Sullivan ◽

M G Elder

Keyword(s):

Arachidonic Acid ◽

Platelet Aggregation ◽

Platelet Activating Factor ◽

Pregnancy Induced Hypertension ◽

Reversible Aggregation ◽

Induced Hypertension ◽

20 Nm ◽

Aggregation Of Platelets ◽

Normotensive Pregnancy

SummaryThe aggregation of platelets from women with pregnancy-induced hypertension (P.I.H.), or with normal pregnancies, in response to arachidonic acid, ADP, collagen or platelet activating factor (PAF) was examined. No differences in platelet aggregation between the normotensive and hypertensive women were detected when arachidonic acid or collagen were used to stimulate in vitro platelet aggregation. Higher concentrations of ADP and PAF were required to aggregate platelets from women with P.I.H. compared with platelets from normotensive controls. Platelets from women with normotensive pregnancies (n = 80) aggregated maximally in response to 20 nM PAF without exception. Reversible aggregation by platelets from women with P.I.H. (n = 25) was observed at the same concentration of PAF; again, this was found in all subjects tested. These results indicate that PAF at a concentration of 20 nM can clearly demonstrate differences in aggregation of platelets from women with normotensive pregnancy and women with P.I.H.

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Inflammation-induced changes in arachidonic acid metabolism in cat lower esophageal sphincter (LES)

Gastroenterology ◽

10.1016/s0016-5085(01)81088-x ◽

2001 ◽

Vol 120 (5) ◽

pp. A219-A219

Author(s):

L CHENG ◽

W CAO ◽

K HARNETT ◽

J BEHAR ◽

P BIANCANI

Keyword(s):

Arachidonic Acid ◽

Lower Esophageal Sphincter ◽

Acid Metabolism ◽

Arachidonic Acid Metabolism ◽

Esophageal Sphincter ◽

Induced Changes

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Increased Response to Arachidonic Acid and U-46619 and Resistance to Inhibitory Prostaglandins in Patients with Chronic Myeloproliferative Disorders

Thrombosis and Haemostasis ◽

10.1055/s-0038-1642568 ◽

1988 ◽

Vol 59 (01) ◽

pp. 073-076 ◽

Cited By ~ 9

Author(s):

Sergio Cortelazzo ◽

Monica Galli ◽

Donatella Castagna ◽

Piera Viero ◽

Giovanni de Gaetano ◽

...

Keyword(s):

Bone Marrow ◽

Arachidonic Acid ◽

Platelet Aggregation ◽

Myeloproliferative Disorders ◽

Bone Marrow Stem Cell ◽

Healthy Controls ◽

Aggregation Response ◽

Thrombotic Complications ◽

Cyclic Endoperoxide ◽

Marrow Stem Cell

SummaryIn patients with myeloproliferative disorders (MPD) a group of related diseases of the bone marrow stem cell and recurrent haemorrhagic and/or thrombotic complications, the production of aggregating prostaglandins (PGs) may be normal or slightly reduced, while PGI2 production is normal. However, MPD platelet sensitivity to antiaggregatory PGs is still unknown.We studied the potency of PGD2, PGI2 and PGEi as inhibitors of platelet aggregation induced by threshold aggregating concentrations of arachidonic acid and U-46619-analogue of the cyclic endoperoxide PGH2 in 20 patients with MPD in comparison with healthy controls, with the aim of evaluating the sensitivity of MPD platelets to antiaggregatory PGs. In these patients platelet prostanoid metabolism was normal. However, the functional response of platelets to aggregating and antiaggregating prostanoids was shifted towards potentially increased platelet aggregation response. These findings could have a clinical relevance in view of the haemostatic and thrombotic complications so frequent in MPD.

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Involvement of Cyclooxygenase- and Lipoxygenase-Mediated Conversion of Arachidonic Acid in Controlling Human Vascular Smooth Muscle Cell Proliferation

Thrombosis and Haemostasis ◽

10.1055/s-0038-1645212 ◽

1990 ◽

Vol 63 (02) ◽

pp. 291-297 ◽

Cited By ~ 28

Author(s):

Herm-Jan M Brinkman ◽

Marijke F van Buul-Worteiboer ◽

Jan A van Mourik

Keyword(s):

Cell Proliferation ◽

Arachidonic Acid ◽

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cells ◽

Smooth Muscle Cell ◽

Muscle Cell ◽

Vascular Smooth Muscle Cell ◽

Muscle Cells ◽

Smooth Muscle Cell Proliferation

SummaryWe observed that the growth of human umbilical arterysmooth muscle cells was inhibited by the phospholipase A2 inhibitors p-bromophenacylbromide and mepacrine. Thesefindings suggest that fatty acid metabolism might be integrated in the control mechanism of vascular smooth muscle cell proliferation. To identify eicosanoids possibly involved in this process, we studied both the metabolism of arachidonic acid of these cells in more detail and the effect of certain arachidonic acid metabolites on smooth muscle cells growth. We found no evidence for the conversion of arachidonic acid via the lipoxygenase pathway. In contrast, arachidonic acid was rapidly converted via the cyclooxy-genase pathway. The following metabolites were identified: prostaglandin E2 (PGE2), 6-keto-prostaglandin F1α (6-k-PGF1α), prostaglandin F2α (PGF2α), 12-hydroxyheptadecatrienoic acid (12-HHT) and 11-hydroxyeicosatetetraenoic acid (11-HETE). PGE2 was the major metabolite detected. Arachidonic acid metabolites were only found in the culture medium, not in the cell. After synthesis, 11-HETE was cleared from the culture medium. We have previously reported that PGE2 inhibits the serum-induced [3H]-thymidine incorporation of growth-arrested human umbilical artery smooth muscle cells. Here we show that also 11-HETEexerts this inhibitory property. Thus, our data suggeststhat human umbilical artery smooth muscle cells convert arachidonic acid only via the cyclooxygenase pathway. Certain metabolites produced by this pathway, including PGE2 and 11-HETE, may inhibit vascular smooth muscle cell proliferation.

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Chlorobutanol, a Preservative of Desmopressin, Inhibits Human Platelet Aggregation and Release In Vitro

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647339 ◽

1990 ◽

Vol 64 (03) ◽

pp. 473-477 ◽

Cited By ~ 4

Author(s):

Shih-Luen Chen ◽

Wu-Chang Yang ◽

Tung-Po Huang ◽

Shiang Wann ◽

Che-ming Teng

Keyword(s):

Arachidonic Acid ◽

Platelet Aggregation ◽

Atp Release ◽

Free Calcium ◽

Dependent Manner ◽

Antiplatelet Effect ◽

Human Platelet Aggregation ◽

Acid Pathway ◽

Arachidonic Acid Pathway

SummaryTherapeutic preparations of desmopressin for parenteral use contain the preservative chlorobutanol (5 mg/ml). We show here that chlorobutanol is a potent inhibitor of platelet aggregation and release. It exhibited a significant inhibitory activity toward several aggregation inducers in a concentration- and time-dependent manner. Thromboxane B2 formation, ATP release, and elevation of cytosolic free calcium caused by collagen, ADP, epinephrine, arachidonic acid and thrombin respectively were markedly inhibited by chlorobutanol. Chlorobutanol had no effect on elastase- treated platelets and its antiplatelet effect could be reversed. It is concluded that the antiplatelet effect of chlorobutanol is mainly due to its inhibition on the arachidonic acid pathway but it is unlikely to have a nonspecitic toxic effect. This antiplatelet effect of chlorobutanol suggests that desmopressin, when administered for improving hemostasis, should not contain chlorobutanol as a preservative.

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