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.

Dipyridamole Inhibits Platelet Aggregation in Whole Blood

1983 ◽  
Vol 50 (04) ◽  
pp. 852-856 ◽  
Author(s):  
P Gresele ◽  
C Zoja ◽  
H Deckmyn ◽  
J Arnout ◽  
J Vermylen ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Significant Negative Correlation ◽  
Significant Inhibition ◽  
Oral Drug ◽  
Human Blood Samples ◽  
Induced Aggregation

SummaryDipyridamole possesses antithrombotic properties in the animal and in man but it does not inhibit platelet aggregation in plasma. We evaluated the effect of dipyridamole ex vivo and in vitro on platelet aggregation induced by collagen and adenosine- 5’-diphosphate (ADP) in human whole blood with an impedance aggregometer. Two hundred mg dipyridamole induced a significant inhibition of both ADP- and collagen-induced aggregation in human blood samples taken 2 hr after oral drug intake. Administration of the drug for four days, 400 mg/day, further increased the antiplatelet effect. A significant negative correlation was found between collagen-induced platelet aggregation in whole blood and dipyridamole levels in plasma (p <0.001). A statistically significant inhibition of both collagen (p <0.0025) and ADP-induced (p <0.005) platelet aggregation was also obtained by incubating whole blood in vitro for 2 min at 37° C with dipyridamole (3.9 μM). No such effects were seen in platelet-rich plasma, even after enrichment with leukocytes. Low-dose adenosine enhanced in vitro inhibition in whole blood.Our results demonstrate that dipyridamole impedes platelet aggregation in whole blood by an interaction with red blood cells, probably involving adenosine.

Lu 23051, A New Potent Inhibitor Of Platelet Aggregation

1981 ◽  
Author(s):  
H D Lehmann ◽  
J Gries ◽  
D Lenke
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Coronary Vessels ◽  
Inhibitory Effect ◽  
Spontaneously Hypertensive ◽  
Dependent Inhibition ◽  
Induced Aggregation

6- [p-(2-(Chiorpropionylamino)phenyl] -4.5-dihydro-5-methyl-3(2H)-pyridazinone, LU 23051, is primarily characterized by its strong inhibition of platelet aggregation under in vitro and in vivo conditions. In vitro there is a concentration-dependent inhibition of ADP and collagen induced aggregation in platelet rich plasma of man, rat and dog. The inhibitory concentration EC 33 % is 0.0010-0.030 mg/1 (man: ADP-0.030, col 1.-0.013 mg/l) depending on species and type of aggregation. When administered orally in ex vivo experiments on rats and dogs the substance is found to have a dose-dependent antiaggregatory effect in the range from 0.1-3.16 mg/kg. The ED 33 % is 0.27-0.63 mg/kg.-In addition after oral administration the substance has a good inhibitory effect in models being based on intravascular platelet aggregation. Thus, a dose of 1 mg/kg inhibits laser-induced aggregation in mesenteric venules of rats. Mortality after i.v. injection of collagen in mice is reduced by 50 % after a dose of 0.02 mg/kg. A dose of 0.039 mg/kg prolongs the bleeding time of rats by 50 %. The aggregation-inhibiting action is of long duration (0.1 mg/kg p.o.∼24 h). The substance does not interfere with clotting.Besides its effect on platelet aggregation LU 23051 acts as vasodilatator as well. Dilatation of coronary vessels by 100 % is seen in isolated guinea-pig hearts at a concentration of 0.1 mg/l. In spontaneously hypertensive rats the substance has an anti hypertensive effect. The ED 20 % is 0.36 mg/kg p.o.The combination of antiaggregatory and vasodilatatory effects opens up interesting aspects with respect to the pharmacotherapeutic use of the new substance

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.

Inhibition of Human Platelet Aggregation by the Proteolytic Effect of Streptokinase (SK). Role of the Factor VIII Related Antigen

1975 ◽  
Author(s):  
R. Castillo ◽  
S. Maragall ◽  
J. A. Guisasola ◽  
F. Casals ◽  
C. Ruiz ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Factor Viii ◽  
Platelet Rich Plasma ◽  
Gel Filtration ◽  
Inhibitory Effect ◽  
Factor Viii Related Antigen ◽  
Human Factor Viii ◽  
Induced Aggregation

Defective ADP-induced platelet aggregation has been observed in patients treated with streptokinase. This same effect appears “in vitro” when adding SK to platelet rich plasma (PRP). Classic hemophilia and normal platelet poor plasmas (PPP) treated with SK inhibit the aggregation of washed platelets; plasmin-treated normal human serum also shows an inhibitory effect on platelet aggregation. However, von Willebrand SK-treated plasmas do not inhibit the aggregation of washed platelets. The same results appear when plasmas are previously treated with a rabbit antibody to human factor VIII.This confirms that the antiaggregating effect is mainly linked to the digested factor VIII related antigen.The inhibition of ADP-induced platelet aggregation has been proved in gel filtration-isolated and washed platelets from SK-treated PRP.Defective ristocetin-induced platelet aggregation has also been observed- This action does not appear in washed platelets from SK-treated PRP in presence of normal PPP, but it does in presence of SK-treated PPP, which suggests that the inhibition of the ristocetin-induced aggregation is due to the lack of factor VIII and not to the factor VIII-related products.Heparin, either “in vivo” or “in vitro”, has corrected the antiaggregating effect of SK.

The pharmacology of L-670,596, a potent and selective thromboxane/prostaglandin endoperoxide receptor antagonist

1989 ◽  
Vol 67 (9) ◽  
pp. 989-993 ◽  
Author(s):  
A. W. Ford-Hutchinson ◽  
Y. Girard ◽  
A. Lord ◽  
T. R. Jones ◽  
M. Cirino ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Guinea Pig ◽  
Receptor Antagonist ◽  
Competitive Inhibition ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Prostaglandin Endoperoxide ◽  
Induced Aggregation

L-670,596 ((−)6,8-difluoro-9-p-methylsulfonyl benzyl-1,2,3,4-tetrahydrocarbazol-1-yl-acetic acid) has been shown to be a potent receptor antagonist as evidenced by the inhibition of the binding of 125I-labeled PTA-OH to human platelets (IC50, 5.5 × 10−9 M), inhibition of U-44069 induced aggregation of human platelet rich plasma (IC50, 1.1 × 10−7 M), and competitive inhibition of contractions of the guinea pig tracheal chain induced by U-44069 (pA2,9.0). The compound was also active in vivo as shown by inhibition of arachidonic acid and U-44069 induced bronchoconstriction in the guinea pig (ED50 values, 0.04 and 0.03 mg/kg i.v., respectively), U-44069 induced renal vasoconstriction in the pig (ED50, 0.02 mg/kg i.v.), and inhibition of ex vivo aggregation of rhesus monkey platelets to U-44069 (active 1–5 mg/kg p.o.). The selectivity of the compound was indicated by the failure to inhibit, first, ADP-induced human or primate platelet aggregation and, second, bronchoconstriction in the guinea pig in vivo and contraction of the guinea pig tracheal chain in vitro to a variety of agonists. It is concluded that L-670,596 is a potent, selective, orally active thromboxane A2/prostaglandin endoperoxide receptor antagonist.Key words: thromboxane A2, thromboxane antagonist, prostaglandin endoperoxides, platelet aggregation.

Pharmacological Profile of DZ-697b, a Novel Anti-Platelet Agent -Selective Inhibitor of vWF- and Collagen-Induced Platelet Aggregation.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1875-1875 ◽  
Author(s):  
Yoshiyasu Ogihara ◽  
Sumie Muramatsu ◽  
Yuki Kaneda ◽  
Takako Iijima ◽  
Tomoko Shibutani ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Guinea Pigs ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Bleeding Risk ◽  
Selective Inhibitor ◽  
Pharmacological Profile ◽  
Induced Aggregation

Abstract Introduction: Bleeding risk accompanied with anti-platelet drugs is an ultimate dilemma in the treatment of thrombosis patient. Under high shear condition of blood flow, vWF- and collagen-induced signaling pathways are likely to trigger the platelet adhesion to the injured endothelium, which leads to the activation of platelets and arterial thrombus formation. Thus, the recent studies suggest that the selective inhibitor of these pathways is a new target of anti-platelet drugs with lower bleeding risk. We report here a pharmacological profile of DZ-697b, which selectively inhibits platelet aggregation evoked by ristocetin and collagen in vitro and ex vivo. Materials and methods: Human volunteers blood was processed platelet rich plasma (PRP) or washed platelets. PRP aggregation was induced by ristocetin and collagen. To reveal the selectivity, effect of DZ-697b on U46619 (TXA2 analogue), ADP, thrombin and TRAP induced aggregation in the washed platelets were examined. In guinea pigs and cynomolgus monkeys, effects of DZ-697b given orally were also examined on ex vivo PRP aggregation induced by collagen. To investigate the underlying mechanisms of DZ-697b, changes in phosphorylation of FcR γ chain, a common signaling pathway of both vWF- and collagen-induced platelet aggregation, were studied. Results: DZ-697b potently inhibited both ristocetin- and collagen-induced human PRP aggregation, the IC50 being 0.74 μM and 0.55 μM, respectively. In contrast, DZ-697b even at 50 μM did not show any influences on U46619, ADP, thrombin and TRAP induced platelet aggregation. DZ-697b did not affect ovine COX-1 and COX-2 activities at up to 300 μM. The bioavailability of this compound was more than 80% in monkeys. Oral administration of DZ-697b at 1–3 mg/kg significantly and persistently inhibited collagen induced PRP aggregation in monkeys and guinea pigs. Application of ristocetin, vWF, and collagen significantly increased the intensity of phosphorylation of FcR γ chain in washed platelets, which were inhibited by DZ-697b. Conclusion: DZ-697b is an orally active compound which selectively inhibits ristocetin- and collagen-induced platelet aggregation and seems to be promising as novel anti-platelet drug.

SELECTIVE ANTAGONISTS OF PAF: INTERFERENCE WITH PLATELET FUNCTION AND EFFECT ON THROMBOGENESIS INDUCED BY SUBENDOTHELIUM.

1987 ◽  
Author(s):  
P Hadvary ◽  
H R Baumgartner
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Blood Platelets ◽  
Rabbit Aorta ◽  
Constant Infusion ◽  
Induced Aggregation

Platelet activating factor (PAF) is a very potent excitatory agonist of blood platelets but the physiological importance of this mediator in platelet thrombus formation is not known. We investigated the effect of two chemically unrelated selective inhibitors of PAF-induced platelet aggregation on thrombogenesis induced by rabbit aorta subendothelium (SE) using an ex vivo perfusion system.Ro 19-3704 is a highly potent inhibitor structurally related to PAF. This compound inhibits PAF-induced aggregation of rabbit platelets in platelet rich plasma in vitro competitively. Against 4 nM PAF, a concentration resulting in submaximal platelet aggre-gregation velocity, the IC50 was 70 nM. Inhibition was highly selective for PAF-induced aggregation, since aggregation induced by collagen (HORM, 5 yg/ml), ADP (1 yM) or thrombin (0.4 U/ml) was not inhibited even at a concentration as high as 10 yM. Bro-tizolam, a triazolobenzodiazepine reported to be a selective inhibitor of PAF-induced platelet activation, had in our system an IC50 of 200 nM. The selective benzodiazepine antagonist Ro 151788 was without effect on inhibition of PAF-induced platelet activation by brotizolam.Ro 19-3704 was given intravenously to rabbits as a bolus of 0.2 mg/kg followed by constant infusion of 0.02 mg/kg/min. This dosage provoked ex vivo a constant right shift ratio of the dose response curve for PAF-induced aggregation (RSR[PAF]) by a factor of 25 to 35. Brotizolam was given orally at a dose of 100 mg/ kg together with 300 mg/kg of Ro 15-1788 (to antagonize the central effects) 90 minutes before starting the perfusion experiment, resulting in a RSR[PAF] of 35 to 135. ADP induced platelet aggregation was not impaired by either compound. SE was exposed to the non-anticoagulated blood withdrawn from the carotid artery for 3 min at 2600 s-1 and for 20 min at 200 s-1 shear rate. Quantitative morphometric evaluation showed that SE coverage by platelets and by fibrin, thrombus area and thrombus height were all unchanged by the PAF antagonists at low and at high shear rates despite a very substantial inhibition of PAF-induced platelet aggregation. Therefore a major role of PAF in SE-induced thrombogenesis seems unlikely.

ETHANOL INHIBITS RABBIT PLATELET RESPONSES TO COLLAGEN IN VITRO BUT DOES NOT AFFECT RABBIT PLATELET ADHERENCE TO DE-ENDOTHELIALIZED A0RTAE IN VIVO

1987 ◽  
Author(s):  
M L Rand ◽  
H M Groves ◽  
R L Kinlough-Rathbone ◽  
M A Packham ◽  
J F Mustard
Keyword(s):  
Coronary Heart Disease ◽  
Heart Disease ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Platelet Adherence ◽  
Induced Aggregation

Epidemiological studies indicate that moderate consumption of alcohol is associated with a reduced risk of coronary heart disease, but it is not known whether inhibition of platelet functions by ethanol is involved. We studied the effects of ethanol on rabbit platelet responses to collagen in vitro and in vivo. Addition of ethanol (4 mg/ml) to suspensions of washed platelets prelabelled with [14c]serotonin inhibited aggregation and secretion in response to low (0.4 μg/ml) concentrations of acid soluble collagen (14% secretion without ethanol, 3% secretion with ethanol). With a higher concentration of collagen (1.25 μg/ml), 4 mg/ml ethanol had no inhibitory effect. The inhibitory effect of ethanol on collagen-induced aggregation was also observed in citrated platelet-rich plasma (c-PRP) to which ethanol was added in vitro and in c-PRP from rabbits given ethanol acutely by gavage (3.5 g/kg) 30 min before blood sampling. The accumulation of [51cr]-labeled platelets on the subendothelium of rabbit aortae de-endothelialized with balloon catheters was measured in vivo in rabbits given ethanol (blood ethanol concentration at time of vessel wall injury: 4.1 ± 0.2 mg/ml, mean ± S.E., n=6). Ten min after de-endothelialization, there was no difference between the number of platelets adherent per square mm of injured aorta of control rabbits (39,400 ± 2,600, mean ± S.E., n=6) and intoxicated rabbits (36,800 ± 3,700, mean ± S.E., n=6). Thus, although ethanol inhibits platelet aggregation and secretion in response to collagen in vitro and ex vivo, it does not alter platelet adherence to the subendothelium, including its constituent collagen, in vivo. Therefore, it is unlikely that ethanol exerts its beneficial effects against coronary heart disease by altering the initial adherence of platelets to injured vessel walls.

Phospholipase C from Clostridium Perfringens Induces Human Platelet Aggregation in Plasma

1988 ◽  
Vol 59 (02) ◽  
pp. 236-239 ◽  
Author(s):  
Giovanna Barzaghi ◽  
Chiara Cerletti ◽  
Giovanni de Gaetano
Keyword(s):  
Platelet Aggregation ◽  
Receptor Antagonist ◽  
Phospholipase C ◽  
Clostridium Perfringens ◽  
Human Platelet ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Platelet Activating Factor ◽  
Inhibitory Effect ◽  
Thromboxane Receptor Antagonist

SummaryWe studied the aggregating effect of different concentrations of phospholipase C (PLC) (extracted from Clostridium perfringens) on human platelet-rich plasma (PRP). PRP was preincubated with PLC for 3 min at 37° C and the platelet aggregation was followed for 10 min. The threshold aggregating concentration (TAG) of PLC was 3-4 U/ml.We also studied the potentiation of PLC with other stimuli on platelet aggregation. Potentiating stimuli, such as arachidonic acid (AA), ADP. Platelet Activating Factor (PAF) and U-46619 (a stable analogue of cyclic endoperoxides) were all used at subthreshold concentrations. We also studied the possible inhibitory effect of aspirin, apyrase, TMQ, a prostaglandin endoper- oxide/thromboxane receptor antagonist and BN-52021, a PAF receptor antagonist. Only aspirin and apyrase were able to reduce aggregation induced by PLC alone and PLC + AA and PLC + ADP respectively. TMQ and BN-52021 were inactive. In ex vivo experiments oral aspirin (500 mg) partially inhibited platelet aggregation induced by PLC alone, PLC + AA and PLC + ADP 2 and 24 h after administration. Aspirin 20 mg for 7 days also reduced aggregation induced by PLC + AA.

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.

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