Interactions Between Blood Platelets and Vascular Endothelium in vitro Studies

1979 ◽  
Author(s):  
M.A. Gimbrone ◽  
K.D. Curwen ◽  
R. I. Handin
Keyword(s):  
Platelet Aggregation ◽  
Vascular Endothelium ◽  
Potent Inhibitor ◽  
Platelet Reactivity ◽  
Blood Platelets ◽  
Primary Cultures ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Platelet Adherence

Endothelial cells (EC) can actively influence the hemostatic response at sites of vascular injury through multiple mechanisms. For example, EC can degrade adenosine diphosphate, release plasminogen activator, and synthesize prostacyclin (PGI2), a potent inhibitor of platelet aggregation. We have examined whether PGI2 also might account for the normal lack of platelet adherence to the uninjured EC surface. In a monolayer adherence assay, radiolabeled human platelets in citrated plasma showed minimal interaction with primary cultures of human EC (<1 platelet adhering per cell). Platelets from aspirin-treated and untreated donors behaved similarly. However, aspirin pretreatment of EC consistently resulted in ~2-fold increases in platelet adherence which could be completely abolished by exogenous PGI2 (0.5–1.0 μg/ml). SV40-transformed human EC (SVHEC), which are deficient in PGI2 production compared to primary EC, showed 10-30 times more platelet adherence. Exogenous PGI2 produced a dose - related (.001-1.0 μg/ml) decrease in platelet adherence to SVHEC but did not result in the basal levels observed with normal EC monolayers. These data suggest that : 1) In addition to its effects on platelet aggregation, PGI2 can influence platelet endothelial cell interactions; 2) The increased platelet reactivity of transformed EC is associated with, but not completely attributable, to decreased PGI2 production; and 3) Factors other than PGI2 may play a role in the thromboresistance of normal vascular endothelium.

scholarly journals Survival and recovery of human platelets stored for five days in a non- plasma medium

Blood ◽  
1986 ◽  
Vol 67 (3) ◽  
pp. 672-675 ◽  
Author(s):  
GA Adams ◽  
SD Swenson ◽  
G Rock
Keyword(s):  
Platelet Aggregation ◽  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Plasma Medium ◽  
Release Reaction ◽  
In Vivo Recovery ◽  
Human Blood Platelets

Abstract Human blood platelets were stored for five days as concentrates in 60 mL of: (a) plasma; (b) non-plasma medium with anticoagulant; and (c) non-plasma medium without anticoagulant. All preparations were equally functional when tested for platelet aggregation and release reaction in response to single agonist or synergistic pairs of agonists in vitro. Platelets stored in non-plasma medium with anti-coagulant had lower kallikrein, fibrino(gen)peptide A, lactate, and beta-thromboglobulin than did plasma controls after five days. In vivo recovery and survival of platelets stored in non-plasma medium with anticoagulant were 51.2% +/- 4.3% and 8.7 +/- 0.3 days, respectively, which were not statistically different from plasma controls of 39.2% +/- 4.9% and 7.2 +/- 0.8 days, respectively. It is concluded that platelets can be stored for five days in a non-plasma medium and still have good in vivo recoveries and survivals.

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.

Possible Mode of Action of Ticlopidine: A Novel Inhibitor of Platelet Aggregation

1979 ◽  
Author(s):  
H. Johnson ◽  
J. B. Heywood
Keyword(s):  
Platelet Aggregation ◽  
Mode Of Action ◽  
Potent Inhibitor ◽  
Platelet Reactivity ◽  
Inhibitory Effect ◽  
Thromboxane Synthetase ◽  
Sustained Effect ◽  
Dependent Inhibition

Ticlopidine (T) is weakly active in vitro, but is a potent inhibitor of platelet aggregation induced by ADP, collagen, thrombin, adrenaline, arachidonic acid, prostaglandin (PG) endoperoxide and thromboxane A2 with a sustained effect, when administered to a variety of animal species, including man. Platelets from treated animals were normal in ultrastructure and 14C-ADP binding was not modified by T. Basal PG synthesis was unaffected, whereas aspirin (A) had a marked inhibitory effect. Platelet cyclo-oxygenase and thromboxane synthetase activities were 90.6±12.9 and 96.1±5.3% of control following T treatment. In contrast to A, T had no effect on vascularprostacyclin (PGI2) synthesis, this being 1.4±0.1, 0.5±0.1 and 1.3±0. 3ng/mg wet weight aorta in T and A-treated and control animals respectively. Platelets from T-treated rats were significantly more responsive to inhibition by exogenous PGI2 (0.2-4 ng/ml) and PGE1 (4- 20 ng/ml). when compared with controls. T administration (30-300 mg/kg) resulted in a dose-dependent inhibition of ADP-induced platelet aggregation (26.0- 87. 5%) and enhancement of platelet reactivity to PGI2 (37.0-159.8%). There was a good correlation between these parameters (r=+0.994). T is a potent inhibitor of platelet aggregati on with a novel mode of action. It is not aspirin-like, but may act to potentiate endogenous PGI2 in vivo, possibly through an effect on platelet adenylate cyclase.

Monosubstituted Coumarins Inhibit Epinephrine-Induced Platelet Aggregation Antiplatelet Effect of Monosubstituted Coumarins

2021 ◽  
Vol 19 ◽  
Author(s):  
Fausto Alejandro Jiménez-Orozco ◽  
Sergio Galicia-Zapatero ◽  
Edgar López-López ◽  
José L. Medina-Franco ◽  
Fernando León Cedeño ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
In Silico ◽  
Drug Targets ◽  
Platelet Reactivity ◽  
Antiplatelet Agents ◽  
Human Platelets ◽  
In Silico Studies ◽  
Vitro Effect ◽  
Induced Aggregation

Aim: Evaluate the in vitro effect of coumarin and 15 monosubstituted derivatives on the inhibition of human platelet aggregation induced by various pro-aggregatory agonists, particularly by epinephrine. Background: The emergence of residual platelet reactivity during the use of conventional antiplatelet agents (acetylsalicylic acid and clopidogrel) is one of the main causes of double therapy´s therapeutic failure. Platelet adrenoceptors participate in residual platelet reactivity. Therefore, it is necessary to develop new antiplatelet agents that inhibit epinephrine-induced platelet aggregation as a new therapeutic strategy. Information on the antiplatelet activity of coumarins in inhibiting epinephrine-induced aggregation is limited. Objective: Establish the structure-activity relationship (SAR) of coumarin derivatives with hydroxy, methoxy, and acetoxy groups in different positions of the coumarin nucleus to identify the most active molecules. Using in silico studies, suggest potential drug targets to which the molecules bind to produce antiplatelet effects. Methods: The platelet aggregation was performed using a Lumi-aggregometer; the inhibitory activity of 16 compounds were evaluated by inducing the aggregation of human platelets (250 × 103/μl) with epinephrine (10 µM), collagen (2 µg / ml) or ADP (10 µM). The aggregation of controls platelets was considered 100% of the response for each pro-aggregatory agonists. Results: Eleven molecules inhibited epinephrine-induced aggregation, with 3-acetoxycoumarin and 7-methoxycoumarin being the most active. Only coumarin inhibited collagen-induced platelet aggregation, but no molecule showed activity when using ADP as an inducer. Conclusions : In silico studies suggest that most active molecules might have antagonistic interactions in the adrenoceptors α2 and β2. The antiplatelet actions of these coumarins have the potential to reduce residual platelet reactivity and thus contribute to the development of future treatments for patients who do not respond adequately to conventional agents.

scholarly journals Effect of propranolol on platelet function

Blood ◽  
1977 ◽  
Vol 49 (2) ◽  
pp. 185-196 ◽  
Author(s):  
BB Weksler ◽  
M Gillick ◽  
J Pink
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Direct Action ◽  
Blood Platelets ◽  
Adenosine Diphosphate ◽  
Ionophore A23187 ◽  
Atherosclerotic Vascular Disease ◽  
Clot Retraction

Abstract Excessive reactivity of blood platelets may contribute to atherosclerotic vascular disease. Hence drugs which alter platelet function may be protective. Prompted by findings that propranolol therapy normalized hyperactive platelet aggregation in patients with coronary artery disease, we studied propranolol in vitro to assess its action on platelets. At concentrations similar to those achieved in vivo (0.1–1 muM), propranolol raised the thresholds for aggregation of some normal paltelets by adenosine diphosphate (ADP). At higher concentrations (10-50 muM), propranolol abolished the second wave of platelet aggregation induced by ADP and epinephrine, and inhibited aggregation induced by collagen, thrombin, and the ionophore A23187. Propanolol blocked the release of 14C-serotonin from platelets, inhibited platelet adhesion to collagen, and interfered with clot retraction. Propranolol blocked ionophore-induced uptake of 45Ca by platelets. Inhibition appeared unrelated to beta-adrenergic blockage, as d(+) propranolol (which lacks beta-blocking activity) was equipotent with 1(-) propranolol. Moreover, practolol, a beta-blockading drug which is nonlipophilic, did not inhibit platelet function. These studies suggested that propranolol, like local anesthetics, decreased platelet responsiveness by a direct action on the platelet membrane, possibly by interfering with calcium availability. Modulation of platelet function by propranolol may occur at concentrations achieved at usual clinical doses of the drug.

scholarly journals Survival and recovery of human platelets stored for five days in a non- plasma medium

Blood ◽  
1986 ◽  
Vol 67 (3) ◽  
pp. 672-675 ◽  
Author(s):  
GA Adams ◽  
SD Swenson ◽  
G Rock
Keyword(s):  
Platelet Aggregation ◽  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Plasma Medium ◽  
Release Reaction ◽  
In Vivo Recovery ◽  
Human Blood Platelets

Human blood platelets were stored for five days as concentrates in 60 mL of: (a) plasma; (b) non-plasma medium with anticoagulant; and (c) non-plasma medium without anticoagulant. All preparations were equally functional when tested for platelet aggregation and release reaction in response to single agonist or synergistic pairs of agonists in vitro. Platelets stored in non-plasma medium with anti-coagulant had lower kallikrein, fibrino(gen)peptide A, lactate, and beta-thromboglobulin than did plasma controls after five days. In vivo recovery and survival of platelets stored in non-plasma medium with anticoagulant were 51.2% +/- 4.3% and 8.7 +/- 0.3 days, respectively, which were not statistically different from plasma controls of 39.2% +/- 4.9% and 7.2 +/- 0.8 days, respectively. It is concluded that platelets can be stored for five days in a non-plasma medium and still have good in vivo recoveries and survivals.

Interaction of Bacterial Endotoxin and Liquoid with Blood Platelets: Aggregation and Decrease in the Electrokinetic Charge

1969 ◽  
Vol 22 (01) ◽  
pp. 192-202 ◽  
Author(s):  
K. A Gröttum ◽  
P. F Hjort ◽  
M Jeremic
Keyword(s):  
Platelet Aggregation ◽  
Electrophoretic Mobility ◽  
Blood Platelets ◽  
Human Platelets ◽  
Dextran Sulphate ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
Very High

SummaryThe effects of Endotoxin and Liquoid on the electrophoretic mobility of human platelets and erythrocytes in vitro and on rabbit platelets and erythrocytes in vivo and in vitro have been investigated.Liquoid reduced the electrophoretic mobility of human platelets to 74% of normal and rabbit platelets to 59% in vitro and to 68% of normal in vivo, while the erythrocytes were unchanged. Liquoid induced massive aggregation of both human and rabbit platelets. In very high concentrations, Liquoid increased the electrophoretic mobility of human platelets and did not induce aggregation.Endotoxin reduced the electrophoretic mobility of rabbit platelets to 83% of normal and aggregated the platelets, but had none of these effects on human platelets.The effects of Endotoxin and Liquoid were inhibited by EDTA, but not by ADPase, suggesting that aggregation was not mediated through ADP.We conclude that Liquoid has the same pattern of effects on the electrokinetic charge of platelets and platelet aggregation as the acid polymeric agents dextran sulphate and heparin. There was good correlation between reduction in the electrokinetic charge of the platelets and platelet aggregation. There were striking similarities between the effects of these agents and Endotoxin.

A Comparative Study of Platelet Aggregation in Man and Laboratory Animals

1970 ◽  
Vol 24 (03/04) ◽  
pp. 385-394 ◽  
Author(s):  
D. C Macmillan ◽  
A. K SIM
Keyword(s):  
Clinical Trials ◽  
Platelet Aggregation ◽  
Comparative Study ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Thromboembolic Disease ◽  
Considerable Importance ◽  
Laboratory Animals ◽  
Platelet Thrombi

SummaryWhen some human platelets were aggregated in vitro by exogenous adenosine diphosphate (ADP) or adrenaline they released their own ADP. As ADP is the final stimulator of most aggregation, this ability to produce its own release gave a self- propagating secondary aggregation (SA) which could be marked in certain individuals and diseased states. In a survey of several animals, this ability to produce self- propagating aggregation was also found in a marked form in cats (which can form systemic platelet thrombo-emboli) and to a less extent in baboons and some dogs. This property of the platelets of humans and cats could be an important factor in their ability to form platelet thrombi more easily than other mammals. Thus, SA and its inhibition by drugs may be of considerable importance in the management of thromboembolic disease and a study of such agents carried out in these animals may be reasonably regarded as a relevant and useful preliminary to clinical trials in man.

scholarly journals Lecithin Analog as a New Platelet Aggregating Agent

1977 ◽  
Author(s):  
J. Hawiqer ◽  
H. W. Hooper
Keyword(s):  
Platelet Aggregation ◽  
Blood Platelets ◽  
Human Platelets ◽  
Phospholipase A ◽  
Synthetic Analog ◽  
Autologous Plasma ◽  
Vitro Effect ◽  
Dose Dependent ◽  
Phospholipase A Inhibitor

Lecithin comprises 32% of the human platelet phospholipids which are the source of arachidonic acid required for biosynthesis of prostaglandin endoperoxides, potent inducers of platelet aggregation. A synthetic analog of lecithin, dimethly-DL-2,3-distearoyloxypropyl-2’-hydroxy-ethylammonium acetate known as a phospholipase A inhibitor, showed a profound in vitro effect upon human platelets. Blood platelets obtained from normal, healthy, fasting volunteers and suspended in autologous plasma aggregated in response to lecithin analog. Platelet aggregation was dose-dependent within the range of 10-5 to 10-4M of lecithin analog and accompanied by release of [3H] serotonin. In contrast, addition of equimolar or higher amounts of lecithin to human platelets in vitro remained without a measurable effect on their function. Sensitivity of human platelets to the lecithin analog used was increased at least 10-fold by separation of platelets from the bulk of plasma proteins by gel filtration on Sepharose 2B. Release of [3H] serotonin from gel-filtered platelets induced by the lecithin analog studied was dose-dependent and partly reversible due to reuptake of serotonin. Thus, the lecithin analog used in our experiments is a new platelet activating agent which is a “false phospholipid” and phospholipase A inhibitor acting through a previously unrecognized mechanism triggering membrane-mediated functions of human platelets.

scholarly journals Interaction of Human Platelets with Subndotrelium: Implications for Measurement of Defects in Platelet Function

1977 ◽  
Author(s):  
V.T. Turitto ◽  
H.J. Weiss ◽  
D.S. Cohen
Keyword(s):  
Platelet Reactivity ◽  
Blood Platelets ◽  
Human Platelets ◽  
Shear Rates ◽  
High Shear Rates ◽  
Contact Adhesion ◽  
Human Blood Platelets ◽  
Low Shear ◽  
Platelet Transport

An in Vitro perfusion technique introduced by Baumgartner has been used to investigate the interaction of human blood platelets with subendothelium of rabbit aortas. Platelet contact, adhesion (spreading) and the formation of ndcxothrombi were measured directly by use of a morphometric technique for a variety of exposure times (1 to 40 min) and a physiological range of flow rates (shear rates varying from 50 to 830 sec-1). A theory accounting for platelet transport through the blood and the platelet reactivity at the vessel surface Indicated platelet transport to be the controlling influence on platelet attachment. Under low shear conditions platelet attachment is unaltered by moderate changes in platelet reactivity. The results suggest that high shear rates (greater than 800 sec-1) are necessary for a sensitive measurement of defects in platelet attachment and that experimental devices which employ low shear conditions are limited in measuring such defects.

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