Mechanism of the Antiplatelet Action of Dipyridamole in Whole Blood: Modulation of Adenosine Concentration and Activity

1986 ◽  
Vol 55 (01) ◽  
pp. 012-018 ◽  
Author(s):  
Paolo Gresele ◽  
Jef Arnout ◽  
Hans Deckmyn ◽  
Jos Vermylen
Keyword(s):  
Platelet Aggregation ◽  
Adenosine Receptor ◽  
Whole Blood ◽  
Blood Cells ◽  
Inhibitory Action ◽  
Phosphodiesterase Inhibitor ◽  
Inhibitory Effect ◽  
Adenosine Concentration ◽  
Pharmacological Studies

SummaryDipyridamole inhibits platelet aggregation in whole blood at lower concentrations than in plasma. The blood cells responsible for increased effectiveness in blood are the erythrocytes. Using the impedance aggregometer we have carried out a series of pharmacological studies in vitro to elucidate the mechanism of action of dipyridamole in whole blood. Adenosine deaminase, an enzyme breaking down adenosine, reverses the inhibitory action of dipyridamole. Two different adenosine receptor antagonists, 5’-deoxy-5’-methylthioadenosine and theophylline, also partially neutralize the activity of dipyridamole in blood. Enprofylline, a phosphodiesterase inhibitor with almost no adenosine receptor antagonistic properties, potentiates the inhibition of platelet aggregation by dipyridamole. An inhibitory effect similar to that of dipyridamole can be obtained combining a pure adenosine uptake inhibitor (RE 102 BS) with a pure phosphodiesterase inhibitor (MX-MB 82 or enprofylline). Mixing the blood during preincubation with dipyridamole increases the degree of inhibition. Lowering the haematocrit slightly reduces the effectiveness.Although we did not carry out direct measurements of adenosine levels, the results of our pharmacological studies clearly show that dipyridamole inhibits platelet aggregation in whole blood by blocking the reuptake of adenosine formed from precursors released by red blood cells following microtrauma. Its slight phosphodiesterase inhibitory action potentiates the effects of adenosine on platelets.

Effect of Dipyridamole on Spontaneous Platelet Aggregation in Whole Blood Decreases with the Time After Venepuncture: Evidence for the Role of ADP

1987 ◽  
Vol 58 (02) ◽  
pp. 744-748 ◽  
Author(s):  
A R Saniabadi ◽  
G D O Lowe ◽  
J C Barbenel ◽  
C D Forbes
Keyword(s):  
Platelet Aggregation ◽  
Correlation Coefficient ◽  
Whole Blood ◽  
Blood Platelet ◽  
Inhibitory Effect ◽  
Time Interval ◽  
Adp Receptor ◽  
Spontaneous Platelet Aggregation

SummarySpontaneous platelet aggregation (SPA) was studied in human whole blood at 3, 5, 10, 20, 30, 40 and 60 minutes after venepuncture. Using a whole blood platelet counter, SPA was quantified by measuring the fall in single platelet count upon rollermixing aliquots of citrated blood at 37° C. The extent of SPA increased with the time after venepuncture, with a correlation coefficient of 0.819. The inhibitory effect of dipyridamole (Dipy) on SPA was studied: (a) 10 μM at each time interval; (b) 0.5-100 μM at 3 and 30 minutes and (c) 15 μM in combination with 100 μM adenosine, 8 μM 2-chloroadenosine (2ClAd, an ADP receptor blocker) and 50 μM aspirin. There was a rapid decrease in the inhibitory effect of Dipy with the time after venepuncture; the correlation coefficient was -0.533. At all the concentrations studied, Dipy was more effective at 3 minutes than at 30 minutes after venepuncture. A combination of Dipy with adenosine, 2ClAd or aspirin was a more effective inhibitor of SPA than either drug alone. However, when 15 μM Dipy and 10 μM Ad were added together, the inhibitory effect of Dipy was not increased significantly, suggesting that Dipy inhibits platelet aggregation independent of Ad. The increase in SPA with the time after venepuncture was abolished when blood was taken directly into the anticoagulant containing 5 μM 2ClAd. It is suggested that ADP released from the red blood cells is responsible for the increased platelet aggregability with the time after venepuncture and makes a serious contribution to the artifacts of in vitro platelet function studies.

EFFECTS OF BLOOD CELLS ON PLATELET AGGREGATION BY IMPEDANCE METHOD

1987 ◽  
Author(s):  
L Mannucci ◽  
R Redaelli ◽  
E Tremoll
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Blood Cells ◽  
White Blood Cells ◽  
Normal Subjects ◽  
Impedance Method ◽  
Induced Aggregation ◽  
Vitro Data ◽  
In Vitro Data

To evaluate the effects of blood cells on the response of platelets to aggregating agents using whole blood impedance aggregometer, studies were carried out on whole blood (WB) of normal subjects and of patients with: polycythemia vera (PV), iatrogenic anemia (IA), primary thrombocytosis (PT), idiopathic thrombotic purpura (ITP), myeloid chronic leukemia (MCL), iatrogenic leukopenia (IL). The in vitro effects of red blood cells (RBC) and of white blood cells (WBC) on platelet rich plasma (PRP) aggregation were also evaluated. WB, PRP, WBC and RBC were prepared by conventional methods. Aggregation was performed using the impedance aggregometer (mod. 540, Chrono Log Corp). In normal subjects the concentration of collagen giving 50 % aggregation (AC50 ) found in PRP did not differ from that of WB, indicating that hematocrit values within the normal range did not appreciably affect platelet aggregation. The results obtained in WB of patients are summarized in the table: In vitro data showed that aggregation in prp in wb of normal subjects was related to the number of platelets present in the sample. RBC added to PRP significant reduced aggregation only when the RBC number was greater than 4.101 cells. No effect of WBC on collagen induced aggregation of PRP was observed, whereas significant inhibition was detected after ADP. It is concluded that the aggregation evaluated in WB with impedance method is dependent on the platelet number. Also, in vitro data and studies in WB of patients indicate that aggregation is significantly affected by the presence of cells other than platelets only in conditions of changes of the ratio between platelets and leukocytes and/or red cells.

THE EFFECT OF COD LIVER OIL INTAKE ON THE STIMULATION OF BLOOD CELLS

1987 ◽  
Author(s):  
J B Hansen ◽  
J O Olsen ◽  
L Wilagård ◽  
B Østerud
Keyword(s):  
Platelet Aggregation ◽  
Young Women ◽  
Whole Blood ◽  
Blood Cells ◽  
In Vitro Model ◽  
Cod Liver Oil ◽  
Blood Samples ◽  
Vitro Model ◽  
Stimulation Of

In an in vitro model, stimulation of blood cells with a low concentration of lipopolysaccharides (LPS) revealed differences between women and men that possibly could be an explanation to why young women have less coronary heart disease than men (see abstract Hansen et al. “A model to--”).This model was also used to study the effect of intake of cod liver oil (CLO). 40 students (20 men and 20 women) were tested followed by an intake of 25 ml CLO daily for 2 months by 20 of the students.Heparinized blood samples were incubated with 2 ng LPS/ ml for 2 hours followed by isolation of plasma for thromboxane B2 and 6-keto-PG 1α quantitation.After the first 2 months period of CLO drinking we have the following results:The two months of CLO intake had no significant effect pn the thromboplastin induced synthesis in monocytes. In addition platelet aggregation was tested in a whole blood aggregometer using ADP addition to heparinized blood or collagen induced platelet aggregation in citrated whole blood. ADP aggregation was reduced from 75.9 ± 16.8% to 55.4 ± 19% in the CLO group of women, whereas the reduction in the CLO group of men was 70.1 ± 17.1% to 60.9±18.6%. Similar result were found with collagen aggregation (57% to 33% for women and 48% to 30% for men).It is concluded that CLO intake reduces TxA2 production and plateletaggregation without having reduced effect on PGI2 production in whole blood.

THE EFFECT OF RED BLOOD CELLS ON PLATELET AGGREGATION IN NORMAL SUBJECTS AND MYELOFIBROTIC PATIENTS

1987 ◽  
Author(s):  
C L Balduini ◽  
G Bertolino ◽  
G Polino ◽  
G Gamba ◽  
F Sinigaglia ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Red Blood Cells ◽  
Whole Blood ◽  
Blood Cells ◽  
Optical Method ◽  
Maximum Rate ◽  
Pathological Condition ◽  
Normal Subjects ◽  
High Concentration

We investigated the effect of red blood cells (RBC) on "in vitro" platelet aggregation by the use of the "Electronic Whole Blood Aggregometer" (Chrono-Log Corporation). Preliminary experiments, studying platelet aggregation in the same PRP by the simultaneous use of the optical method and the electronic method, demonstrated that the maximum rate of impedance changes corre lated well with both the rate and the extent of platelet aggregation as measured by the optical method. The refore, the maximum rate of impedance increase was cho sen for the measurement of platelet aggregation in the presence of different concentrations of RBC. RBC, both at 40 and 60%, significantly inhibited platelet aggregation stimulated by low and high concentration of ADP and epinephrine. Platelet aggregation stimulated by co llagen was slightly reduced only by the higher RBC con centration. The effect of RBC on platelet aggregation was also investigated in idiopathic myelofibrosis, a pathological condition characterized by both platelet and RBC alterations. While on the basis of PRP studies 5 out of 17 patients had hypo-aggregation and 12 had normal aggregation, whole blood studies evidentiated hypo-aggregation in 3 patients, normal aggregation in 4 and spontaneous platelet aggregation (SPA) in 10. SPA was a consequence of platelet abnormality, since it occurred also when platelets from patients were sti rred with normal RBC.In conclusion, RBC may exert different effects on the aggregation of normal and pathological platelets.

GUARANA (Paullinia cupana) INHIBITS AGGREGATION IN WHOLE BLOOD

1987 ◽  
Author(s):  
D A F Chamone ◽  
M Ivany-Silva ◽  
C Cassaro ◽  
G Bellotti ◽  
C Massumoto ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Oral Intake ◽  
Inhibitory Effect ◽  
Impedance Method ◽  
Paullinia Cupana ◽  
Induced Aggregation

Guarana, a methylxanthine obtained from the seeds of Paullinia cupana has been largely used in the Amazon region by native indians during centuries as stimulant. We evaluated the effect of guarana on ex-vivo and in vitro platelet aggregation induced by adenosine-5-diphosphate (ADP) in human and rat whole blood with an impedance (Chrono-Log, model 500) and in their platelet rich plasma (PRP) with an optical aggregometer (Chrono-Log, model 440). Ex-vivo studies were carried out after single oral intake of guarana. Seven healthy volunteers (5 male and 2 female) aged 19-26 years who had taken no drugs for 10 days before, ingested 8gm of crude powder of guarana. Blood samples were drawn before and 1 hour after guarana intake. We observed a significative inhibition of platelet aggregation in whole blood meanwhile PRP was un changed as compared to basal values. In vitro studies were performed in whole blood and PRP from human volunteers and male Wis-tar rats. The combined effect of guarana and adenosine was also studied. A control aggregation was always run with saline. The results demonstrated an inhibition statistically significative (p < 0.001) of platelet aggregation in whole blood. Differently from whole blood the PRP with the same concentration of guarana did not result in inhibition of ADP induced aggregation when eva luated with the impedance method. The blood incubation with adenosine and guarana resulted in synergistic inhibitory effect that was much more strinking in whole blood than in PRP. Guarana fails to inhibit aggregation of rat platelets.Our results demonstrate that guarana prevents platelet aggregation in whole blood which depends on red blood cells, probably involving adenosine.

Inhibitory effects of antibiotics on platelet aggregation in vitro

1997 ◽  
Vol 16 (11) ◽  
pp. 662-666 ◽  
Author(s):  
Hiroko Kariyazono ◽  
Kazuo Nakamura ◽  
Terutoshi Shinkawa ◽  
Yukinori Moriyama ◽  
Hitoshi Toyohira ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Blood Concentration ◽  
Chemical Structure ◽  
Inhibitory Action ◽  
Adenosine Diphosphate ◽  
Inhibitory Effect ◽  
Carboxyl Group ◽  
Inhibitory Effects ◽  
Induced Aggregation

1 We evaluated in vitro inhibitory effects of six types of antibiotic, aztreonam (AZT), cefamandole (CMD), cefmetazole (CMZ), cefotiam (CTM), flomoxef (FMOX) and latamoxef (LMOX), on platelet aggregation, using healthy volunteers' blood. Four types-FMOX, LMOX, CTM and CMD-inhibited, in concentration of 2500 ?g/ml, the secondary aggregation induced by 3.0 ?M adenosine diphosphate (ADP), and also inhibited the aggregation induced by 0.5 ?g/ml collagen. AZT in the same concentration, did not inhibit the aggregation induced by collagen, and it inhibited only ADP induced aggregation. CMZ, in the same concentration, inhibited neither of the two aggregations. 2 The inhibitory effects of the antibiotics on collagen- induced aggregation were dependent on the concen tration of respective antibiotics. When classified by the strength of inhibitory action, LMOX and FMOX were strong, followed by CTM and CMD. The action of AZT and CMZ was weak. In particular, LMOX showed a 32% inhibitory effect at concentration of 50 ?g/ml, a level near the blood concentration obtained with clinical usual dose. 3 No relationship was observed between inhibitory effects of antibiotics on ADP- or collagen-induced aggregation and the presence or absence of carboxyl group and/or N-methyltetrazolethiol group in the chemical structure.

DN 9693: A Phosphodiesterase Inhibitor with a Platelet Membrane Effect

1989 ◽  
Vol 61 (02) ◽  
pp. 266-269 ◽  
Author(s):  
C Jackson ◽  
J Ball ◽  
J Peel ◽  
J Lawry ◽  
M Greaves ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Aggregation ◽  
Platelet Reactivity ◽  
Surface Membrane ◽  
Phosphodiesterase Inhibitor ◽  
Inhibitory Effect ◽  
Platelet Membrane ◽  
Dependent Manner ◽  
Platelet Surface

SummaryWe have examined the in vitro effects of DN 9693 (piperidinylimidazo-quinazolinone) on various aspects of platelet reactivity. Our results are consistent with its known function as a phosphodiesterase inhibitor in that it increased platelet cyclic AMP, particularly in conjunction with an adenylate cyclase stimulator, and exerted a profound inhibitory effect on platelet aggregation responses to a variety of agonists. DN 9693 also inhibited ristocetin-induced platelet agglutination (RIPA). We therefore examined its effect on ristocetin co-factor assays and on the binding of a monoclonal antibody (McAb) to platelet membrane glycoprotein lb (GPIb). The drug inhibited the binding of the monoclonal antibody in a dose-dependent manner. This suggests an effect of the drug on the platelet surface membrane with reduced expression of GPIb. Our results indicate that in addition to its anticipated inhibitory effect on platelet aggregation, DN 9693 may also inhibit platelet adhesion.

Reaction of Acetaldehyde with Human Platelets

1992 ◽  
Vol 67 (01) ◽  
pp. 126-130 ◽  
Author(s):  
Olivier Spertini ◽  
Jacques Hauert ◽  
Fedor Bachmann
Keyword(s):  
Platelet Aggregation ◽  
Inhibitory Action ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Reaction Medium ◽  
Human Platelets ◽  
Membrane Glycoproteins ◽  
Neutral Ph

SummaryPlatelet function defects observed in chronic alcoholics are not wholly explained by the inhibitory action of ethanol on platelet aggregation; they are not completely reproduced either in vivo by short-term ethanol perfusion into volunteers or in vitro by the addition of ethanol to platelet-rich plasma. As acetaldehyde (AcH) binds to many proteins and impairs cellular activities, we investigated the effect of this early degradation product of ethanol on platelets. AcH formed adducts with human platelets at neutral pH at 37° C which were stable to extensive washing, trichloracetic acid hydrolysis and heating at 100° C, and were not reduced by sodium borohydride. The amount of platelet adducts formed was a function of the incubation time and of the concentration of AcH in the reaction medium. At low AcH concentrations (<0.2 mM), platelet bound AcH was directly proportional to the concentration of AcH in the reaction medium. At higher concentrations (≥0.2 mM), AcH uptake by platelets tended to reach a plateau. The amount of adducts was also proportional to the number of exposures of platelets to pulses of 20 pM AcH.AcH adducts formation severely impaired platelet aggregation and shape change induced by ADP, collagen and thrombin. A positive correlation was established between platelet-bound AcH and inhibition of aggregation.SDS-PAGE analysis of AcH adducts at neutral pH demonstrated the binding of [14C]acetaldehyde to many platelet proteins. AcH adduct formation with membrane glycoproteins, cytoskeleton and enzymes might interfere with several steps of platelet activation and impair platelet aggregation.This in vitro study shows that AcH has a major inhibitory action on platelet aggregation and may account for the prolonged ex vivo inhibition of aggregation observed in chronic alcoholics even in the absence of alcoholemia.

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

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.

Inhibition of Platelet Function by Antiarrhythmic Drugs, Verapamil and Disopyramide

1982 ◽  
Vol 47 (02) ◽  
pp. 150-153 ◽  
Author(s):  
P Han ◽  
C Boatwright ◽  
N G Ardlie
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Antiarrhythmic Drugs ◽  
Adenosine Diphosphate ◽  
Inhibitory Effect ◽  
Second Phase ◽  
Ionophore A23187 ◽  
High Concentrations ◽  
Artery Disease

SummaryVarious cardiovascular drugs such as nitrates and propranolol, used in the treatment of coronary artery disease have been shown to have an antiplatelet effect. We have studied the in vitro effects of two antiarrhythmic drugs, verapamil and disopyramide, and have shown their inhibitory effect on platelet function. Verapamil, a calcium channel blocker, inhibited the second phase of platelet aggregation induced by adenosine diphosphate (ADP) and inhibited aggregation induced by collagen. Disopyramide similarly inhibited the second phase of platelet aggregation caused by ADP and aggregation induced by collagen. Either drug in synergism with propranolol inhibited ADP or collagen-induced platelet aggregation. Disopyramide at high concentrations inhibited arachidonic add whereas verapamil was without effect. Verapamil, but not disopyramide, inhibited aggregation induced by the ionophore A23187.

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