Unique coronary vasodilator induction by leukotriene D4

Coronary blood flow (CBF) and myocardial contractility decrease markedly in response to intracoronary administration of leukotriene D4 (LTD4). With steady infusion, however, both CBF and contractility escape, approaching preinfusion values despite ongoing LTD4 administration. To clarify the mechanism of this escape, we reinfused plasma from the coronary vein draining the myocardial area receiving LTD4. Introducing this plasma into a coronary artery caused a marked rise in coronary flow for the duration of the plasma infusion. Coronary flow reduction with vasopressin or mechanical occlusion matching that caused by LTD4 failed to elicit vasodilator production. Thus a unique coronary vasodilator factor is induced by LTD4. Whole blood or platelet-rich plasma incubated with LTD4 in vitro produced the same pattern of coronary dilation on intracoronary infusion; LTD4 incubation with platelet-poor plasma failed to elicit a vasodilation. The vasodilator factor is stable and is not potassium, a prostaglandin, catecholamine, histamine, serotonin, adenosine, adenosine diphosphate, or platelet-activating factor. Production of this leukotriene-induced vasodilator factor may account for the escape from LTD4-induced coronary constriction.

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Haemostatic Platelet Plug Formation in the Isolated Rabbit Mesenteric Preparation - An Analysis of Red Blood Cell Participation

Thrombosis and Haemostasis ◽

10.1055/s-0038-1650069 ◽

1980 ◽

Vol 44 (01) ◽

pp. 006-008 ◽

Cited By ~ 12

Author(s):

D Bergqvist ◽

K-E Arfors

Keyword(s):

Whole Blood ◽

Platelet Rich Plasma ◽

Adenosine Diphosphate ◽

In Vitro Test ◽

Pharmacological Agents ◽

Vitro Test ◽

Releasing Effect ◽

Plug Formation

SummaryIn a model using an isolated rabbit mesenteric preparation microvessels were transected and the time until haemostatic plugs formed was registered. Perfusion of platelet rich plasma gave no haemostasis whereas whole blood did. Addition of chlorpromazine or adenosine to the whole blood significantly prolonged the time for haemostasis, and addition of ADP to the platelet rich plasma significantly shortened it. It is concluded that red cells are necessary for a normal haemostasis in this model, probably by a combination of a haemodynamic and ADP releasing effect.The fundamental role of platelets in haemostatic plug formation is unquestionable but there are still problems concerning the stimulus for this process to start. Three platelet aggregating substances have been discussed – thrombin, adenosine diphosphate (ADP) and collagen. Evidence speaking in favour of thrombin is, however, very minimal, and the discussion has to be focused on collagen and ADP. In an in vitro system using polyethylene tubings we have shown that "haemostasis" can be obtained without the presence of collagen but against these results can be argued that it is only another in vitro test for platelet aggregation (1).To be able to induce haemostasis in this model, however, the presence of red blood cells is necessary. To further study this problem we have developed a model where haemostatic plug formation can be studied in the isolated rabbit mesentery and we have briefly reported on this (2).Thus, it is possible to perfuse the vessels with whole blood as well as with platelet rich plasma (PRP) and different pharmacological agents of importance.

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Fibrinogen-independent aggregation and deaggregation of human platelets: studies in two afibrinogenemic patients

Blood ◽

10.1182/blood.v70.1.221.221 ◽

1987 ◽

Vol 70 (1) ◽

pp. 221-226 ◽

Cited By ~ 25

Author(s):

M Cattaneo ◽

RL Kinlough-Rathbone ◽

A Lecchi ◽

C Bevilacqua ◽

MA Packham ◽

...

Keyword(s):

Platelet Aggregation ◽

Plasma Proteins ◽

Platelet Rich Plasma ◽

Platelet Activating Factor ◽

Adenosine Diphosphate ◽

Human Platelets ◽

Human Fibrinogen ◽

Control Subjects ◽

Platelet Aggregates ◽

And Control

Abstract Platelets from two afibrinogenemic patients were used to determine whether fibrinogen is essential for platelet aggregation and to examine whether released fibrinogen contributes to the stabilization of platelet aggregates when platelets have been induced to aggregate and release their granule contents by stimulation with thrombin. The addition of adenosine diphosphate (ADP) to platelet-rich plasma (PRP) or to suspensions of washed platelets from the afibrinogenemic patients caused the formation of small aggregates, which was either not inhibited or only slightly inhibited by the F(ab')2 fragments of an antibody to fibrinogen but was inhibited by an antibody (10E5) to glycoprotein IIb/IIIa. Thus there is a component of ADP-induced platelet aggregation that is not dependent on fibrinogen or other plasma proteins but is dependent on glycoprotein IIb/IIIa. There was little difference in the extent of aggregation and the release of granule contents of normal and afibrinogenemic platelets in response to the release-inducing agents collagen, platelet-activating factor (PAF), sodium arachidonate, or thrombin. With normal or afibrinogenemic platelets, aggregation by thrombin (0.2 U/mL or higher) was not inhibited by the F(ab')2 fragments of an antibody to human fibrinogen. Deaggregation by combinations of inhibitors of platelets aggregated by 1 U/mL thrombin showed no difference between platelets from afibrinogenemic and control subjects, indicating that released fibrinogen does not make a major contribution to the stabilization of platelet aggregates formed by thrombin stimulation.

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Do patients with thromboembolic disease have circulating platelet aggregates?

Blood ◽

10.1182/blood.v64.1.205.bloodjournal641205 ◽

1984 ◽

Vol 64 (1) ◽

pp. 205-209 ◽

Cited By ~ 1

Author(s):

FH Kohanna ◽

MH Smith ◽

EW Salzman

Keyword(s):

Platelet Rich Plasma ◽

Venous Blood ◽

Adenosine Diphosphate ◽

Normal Subjects ◽

Thromboembolic Disease ◽

Circulating Platelet Aggregates ◽

Platelet Aggregates ◽

Lower Ratio

Reports of circulating platelet aggregates (ie, microemboli) in thromboembolism and other vascular disorders are based on a method (Wu and Hoak , 1974) in which venous blood is collected via scalp vein needle and tubing into either formaldehyde, which fixes aggregates, or EDTA, which disperses them. The ratio of platelet counts in platelet- rich plasma (PRP) from the two blood samples after centrifugation is interpreted as a measure of platelet aggregates in the circulation in vivo. We compared this standard Wu and Hoak technique with a modified one, in which blood was drawn directly into a syringe, and with a third method that avoided centrifugation by counting single platelets in whole blood. Both modified techniques could detect aggregates generated in vitro with adenosine diphosphate (ADP). In 12 normal subjects, the three methods were equivalent, but in 37 patients with thromboembolic disorders, the standard Wu and Hoak method gave a lower ratio than the other methods. Similar results were found in a subset of eight patients with myocardial infarction. Heparin treatment of patients did not influence the results. The data suggest that formation of platelet aggregates occurred during venipuncture. Platelets may be hyperactive in patients with thromboembolic disease and may form aggregates in vitro during collection, but the concept of chronic microembolism in such patients should be reassessed.

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

Thrombosis and Haemostasis ◽

10.1055/s-0038-1653698 ◽

1971 ◽

Vol 26 (03) ◽

pp. 455-466 ◽

Cited By ~ 1

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.

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Impaired cytoplasmic ionized calcium mobilization in inherited platelet secretion defects

Blood ◽

10.1182/blood.v74.2.664.664 ◽

1989 ◽

Vol 74 (2) ◽

pp. 664-672 ◽

Cited By ~ 30

Author(s):

AK Rao ◽

MA Kowalska ◽

J Disa

Keyword(s):

Myosin Light Chain ◽

Direct Evidence ◽

Platelet Rich Plasma ◽

Platelet Activating Factor ◽

Adenosine Diphosphate ◽

Ionophore A23187 ◽

Serotonin Secretion ◽

Intracellular Ca ◽

Normal Controls ◽

Platelet Secretion

Abstract Defects in platelet cytoplasmic Ca++ mobilization have been postulated but not well demonstrated in patients with inherited platelet secretion defects. We describe studies in a 42-year-old white woman, referred for evaluation of easy bruising, and her 23-year-old son. In both subjects, aggregation and 14C-serotonin secretion responses in platelet-rich plasma (PRP) to adenosine diphosphate (ADP), epinephrine, platelet activating factor (PAF), arachidonic acid (AA), U46619, and ionophore A23187 were markedly impaired. Platelet ADP and adenosine triphosphate (ATP), contents and thromboxane synthesis induced by thrombin and AA were normal. In quin2-loaded platelets, the basal intracellular Ca++ concentration, [Ca++]i, was normal; however, peak [Ca++]i measured in the presence of 1 mmol/L external Ca++ was consistently diminished following activation with ADP (25 mumol/L), PAF (20 mumol/L), collagen (5 micrograms/mL), U46619 (1 mumol/L), and thrombin (0.05 to 0.5 U/mL). In aequorin-loaded platelets, the peak [Ca++]i studied following thrombin (0.05 and 0.5 U/mL) stimulation was diminished. Myosin light chain phosphorylation following thrombin (0.05 to 0.5 U/mL) stimulation was comparable with that in the normal controls, while with ADP (25 mumol/L) it was more strikingly impaired in the propositus. We provide direct evidence that at least in some patients with inherited platelet secretion defects, agonist-induced Ca++ mobilization is impaired. This may be related to defects in phospholipase C activation. These patients provide a unique opportunity to obtain new insights into Ca++ mobilization in platelets.

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Fibrinogenolytic afibrinogenemia after envenomation by western diamondback rattlesnake (Crotalus atrox)

Blood ◽

10.1182/blood.v63.1.1.1 ◽

1984 ◽

Vol 63 (1) ◽

pp. 1-14 ◽

Cited By ~ 29

Author(s):

AZ Budzynski ◽

BV Pandya ◽

RN Rubin ◽

BS Brizuela ◽

T Soszka ◽

...

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Plasminogen Activator ◽

Platelet Rich Plasma ◽

Muscle Cells ◽

Adenosine Diphosphate ◽

Crotalus Atrox ◽

Serotonin Secretion ◽

Diamondback Rattlesnake

Abstract The absence of fibrinogen and the presence of plasmic fragments X, Y, D, and E were demonstrated in a patient bitten by a western diamondback rattlesnake, Crotalus atrox. The factor VIII level and the platelet count were within normal limits. There were distinct changes of protease inhibitors in the patient's plasma. Alpha-1-protease inhibitor was elevated. Antithrombin-III was only slightly decreased after the envenomation, but alpha 2-antiplasmin and alpha 2-macroglobulin were initially significantly lowered, returning to normal values in 38 and 3 days, respectively. Plasmin-alpha 2-antiplasmin complex was present until day 10 after the envenomation. However, purified plasminogen was not activated in vitro by the venom. Cultured endothelial and smooth muscle cells from human blood vessels released an increased amount of plasminogen activator upon incubation with the venom. The release did not result from cell lysis. Platelets in normal human platelet-rich plasma were aggregated by 10 micrograms/ml of the venom, without serotonin secretion. The aggregation kinetics and serotonin secretion induced by adenosine diphosphate (ADP) or arachidonate were not significantly affected by the venom at 1–10 micrograms/ml. It is concluded that the predominant mechanism of afibrinogenemia in the patient after Crotalus atrox bite resulted from primary fibrinogenolysis and not from a consumptive coagulopathy. The lytic state seemed to be induced through an indirect activation of plasminogen by vascular plasminogen activator, which was probably released from endothelial cells and smooth muscle cells by the snake venom.

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Surfactants Reduce Platelet–Bubble and Platelet–Platelet Binding Induced by In Vitro Air Embolism

Anesthesiology ◽

10.1097/00000542-200512000-00015 ◽

2005 ◽

Vol 103 (6) ◽

pp. 1204-1210 ◽

Cited By ~ 24

Author(s):

David M. Eckmann ◽

Stephen C. Armstead ◽

Feras Mardini

Keyword(s):

Platelet Rich Plasma ◽

Air Embolism ◽

Adenosine Diphosphate ◽

Molecular Probes ◽

Clinical Role ◽

Platelet Binding ◽

Inverted Microscope ◽

Surface Active ◽

Surface Active Compounds

Background The effect of gas bubbles on platelet behavior is poorly characterized. The authors assessed platelet-bubble and platelet-platelet binding in platelet-rich plasma in the presence and absence of bubbles and three surface-active compounds. Methods Platelet-rich plasma was prepared from blood drawn from 16 volunteers. Experimental groups were surfactant alone, sparging (microbubble embolization) alone, sparging with surfactant, and neither sparging nor surfactant. The surfactants were Pluronic F-127 (Molecular Probes, Eugene, OR), Perftoran (OJSC SPC Perftoran, Moscow, Russia), and Dow Corning Antifoam 1510US (Dow Corning, Midland, MI). Videomicroscopy images of specimens drawn through rectangular glass microcapillaries on an inverted microscope and Coulter counter measurements were used to assess platelet-bubble and platelet-platelet binding, respectively, in calcium-free and recalcified samples. Histamine-induced and adenosine diphosphate-induced platelet-platelet binding were measured in unsparged samples. Differences between groups were considered significant for P < 0.05 using analysis of variance and the Bonferroni correction. Results Sixty to 100 platelets adhered to bubbles in sparged, surfactant-free samples. With sparging and surfactant, few platelets adhered to bubbles. Numbers of platelet singlets and multimers not adherent to bubbles were different (P < 0.05) compared both with unsparged samples and sparged samples without surfactant. No significant platelet-platelet binding occurred in uncalcified, sparged samples, although 20-30 platelets adhered to bubbles. Without sparging, histamine and adenosine diphosphate provoked platelet-platelet binding with and without surfactants present. Conclusions Sparging causes platelets to bind to air bubbles and each other. Surfactants added before sparging attenuate platelet-bubble and platelet-platelet binding. Surfactants may have a clinical role in attenuating gas embolism-induced platelet-bubble and platelet-platelet binding.

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Leukocytes Can Enhance Platelet-mediated Aggregation and Thromboxane Release via Interaction of P-selectin Glycoprotein Ligand 1 with P-selectin

Anesthesiology ◽

10.1097/00000542-200101000-00025 ◽

2001 ◽

Vol 94 (1) ◽

pp. 145-151 ◽

Cited By ~ 49

Author(s):

Nauder Faraday ◽

Robert B. Scharpf ◽

Jeffrey M. Dodd-o ◽

Elizabeth A. Martinez ◽

Brian A. Rosenfeld ◽

...

Keyword(s):

Flow Cytometry ◽

Adenosine Triphosphate ◽

Whole Blood ◽

Platelet Rich Plasma ◽

Adenosine Diphosphate ◽

Live Cells ◽

Vitro Analysis ◽

Blocking Antibodies ◽

Induced Aggregation

Background Platelet--leukocyte conjugates have been observed in patients with unstable coronary syndromes and after cardiopulmonary bypass. In vitro, the binding of platelet P-selectin to leukocyte P-selectin glycoprotein ligand-1 (PSGL1) mediates conjugate formation; however, the hemostatic implications of these cell--cell interactions are unknown. The aims of this study were to determine the ability of leukocytes to modulate platelet agonist--induced aggregation and secretion in the blood milieu, and to investigate the role of P-selectin and PSGL-1 in mediating these responses. Methods Blood was drawn from healthy volunteers for in vitro analysis of platelet agonist--induced aggregation, secretion (adenosine triphosphate, beta-thromboglobulin, and thromboxane), and platelet-leukocyte conjugate formation. Experiments were performed on live cells in whole blood or plasma to simulate physiologic conditions. Whole-blood impedance and optical aggregometry, flow cytometry, and enzyme-linked immunosorbent assays were performed in the presence and absence of blocking antibodies to P-selectin and PSGL1. The platelet-specific agonists, thrombin receptor activating peptide and adenosine diphosphate, were used to elicit platelet activation responses. Results Inhibition of platelet--leukocyte adherence by P- selectin and PSGL1 antibodies decreased agonist--induced aggregation in whole blood. The presence of leukocytes in platelet-rich plasma increased aggregation, and this increase was attenuated by P-selectin blocking antibodies. Data from flow cytometry confirmed that platelet-leukocyte conjugate formation contributed to aggregation responses. Blocking antibodies reduced platelet agonist--induced thromboxane release but had no impact on adenosine triphosphate and beta-thomboglobulin secretion. Conclusions Leukocytes can enhance platelet agonist--induced aggregation and thromboxane release in whole blood and platelet-rich plasma under shear conditions in vitro. Interaction of platelet P-selectin with leukocyte PSGL1 contributes substantially to these effects.

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Dipyridamole Potentiates Platelet Inhibition by Nitric Oxide

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646418 ◽

1991 ◽

Vol 66 (03) ◽

pp. 343-349 ◽

Cited By ~ 29

Author(s):

Hidde Bult ◽

Hermine R L Fret ◽

François H Jordaens ◽

Arnold G Herman

Keyword(s):

Nitric Oxide ◽

Cyclic Gmp ◽

Cell Injury ◽

Ex Vivo ◽

Platelet Rich Plasma ◽

Adenine Nucleotides ◽

Adenosine Diphosphate ◽

Guanosine Monophosphate ◽

Double Blind

SummaryIn a placebo-controlled double blind cross-over experiment the adenosine uptake inhibitor dipyridamole (400 mg/day) did not affect ex vivo platelet aggregation induced by collagen or adenosine-diphosphate (ADP) in an electronic whole blood aggregometer (WBA). Dipyridamole was also inactive in vitro, unless red blood cell injury was deliberately enhanced, thereby increasing the level of free adenine nucleotides. Since dipyridamole also inhibits cyclic guanosine monophosphate (GMP) phosphodiesterase (PDE), we used platelet rich plasma (PRP) to study its interaction with authentic and endothelium-derived nitric oxide (NO). The latter inhibits platelets by increasing cyclic GMP. Dipyridamole (1 to 30 εM), either alone or in combination with a subthreshold concentration of prostacyclin (PGI2), was inactive. However, when combined with a subthreshold concentration of NO, dipyridamole caused a concentration-dependent platelet suppression, which became more pronounced when PGI2 was present as well. It is concluded that dipyridamole could reduce the threshold for platelet suppression by NO through inhibition of cyclic GMP PDE.

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Aggregation of Rabbit Blood Platelets Produced in Vitro by Saline “Extract” of Tendons

Thrombosis and Haemostasis ◽

10.1055/s-0038-1654980 ◽

1963 ◽

Vol 09 (02) ◽

pp. 248-263 ◽

Cited By ~ 42

Author(s):

Torstein Hovig

Keyword(s):

Electron Microscopy ◽

Blood Coagulation ◽

Platelet Rich Plasma ◽

Blood Platelets ◽

Adenosine Diphosphate ◽

Blood Platelet ◽

Saline Extract ◽

Rabbit Blood ◽

Platelet Aggregates

SummaryRabbit blood platelet aggregates were produced in vitro by addition of rabbit tendon “extract” to citrated platelet-rich plasma. The aggregating activity was not due to presence of adenosine diphosphate in the “extracts” and was unrelated to blood coagulation. The aggregating principle was destroyed by heating of the “extract” to 60° C for 15 minutes or by incubation with collagenase for 1 hour at 37° C. The aggregating effect was associated with particles which were sedi- mented by centrifugation for 30 minutes at 10,000 G. By means of electron microscopy the particles were identified as cross-striated collagen fibrils.

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