scholarly journals Effects of the Btk-Inhibitors Remibrutinib (LOU064) and Rilzabrutinib (PRN1008) With Varying Btk Selectivity Over Tec on Platelet Aggregation and in vitro Bleeding Time

2021 ◽  
Vol 8 ◽  
Author(s):  
Rundan Duan ◽  
Luise Goldmann ◽  
Richard Brandl ◽  
Michael Spannagl ◽  
Christian Weber ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
B Cell ◽  
Platelet Activation ◽  
Bleeding Time ◽  
Antiplatelet Drug ◽  
Bleeding Events ◽  
B Cell Malignancies ◽  
Closure Time ◽  
Induced Aggregation

Background: Bruton tyrosine kinase inhibitors (BTKi) are used in B-cell malignancies and in development against various autoimmune diseases. Since Btk is also involved in specific pathways of platelet activation, BTKi might be considered to target platelet GPVI/GPIb-mediated atherothrombosis and platelet FcγRIIA-dependent immune disorders. However, BTKi treatment of patients with B-cell malignancies is frequently associated with mild bleeding events caused possibly by off-target inhibition of Tec. Here, we compared the platelet effects of two novel BTKi that exhibit a high (remibrutinib) or low (rilzabrutinib) selectivity for Btk over Tec.Methods and Results: Remibrutinib and rilzabrutinib were pre-incubated with anticoagulated blood. Platelet aggregation and in vitro bleeding time (closure time) were studied by multiple electrode aggregometry (MEA) and platelet-function analyzer-200 (PFA-200), respectively. Both BTKi inhibited atherosclerotic plaque-stimulated GPVI-mediated platelet aggregation, remibrutinib being more potent (IC50 = 0.03 μM) than rilzabrutinib (IC50 = 0.16 μM). Concentrations of remibrutinib (0.1 μM) and rilzabrutinib (0.5 μM), >80% inhibitory for plaque-induced aggregation, also significantly suppressed (>90%) the Btk-dependent pathways of platelet aggregation upon GPVI, von Willebrand factor/GPIb and FcγRIIA activation stimulated by low collagen concentrations, ristocetin and antibody cross-linking, respectively. Both BTKi did not inhibit aggregation stimulated by ADP, TRAP-6 or arachidonic acid. Remibrutinib (0.1 μM) only slightly prolonged closure time and significantly less than rilzabrutinib (0.5 μM).Conclusion: Remibrutinib and rilzabrutinib inhibit Btk-dependent pathways of platelet aggregation upon GPVI, VWF/GPIb, and FcγRIIA activation. Remibrutinib being more potent and showing a better profile of inhibition of Btk-dependent platelet activation vs. hemostatic impairment than rilzabrutinib may be considered for further development as an antiplatelet drug.

The d-Enantiomer Form of Indobufen Totally Accounts for the Anti-Cyclooxygenase and Antiplatelet Activity Ex Vivo and for the Increase in Bleeding Time by Indobufen in Man

1992 ◽  
Vol 67 (02) ◽  
pp. 258-263 ◽  
Author(s):  
Raffaele De Caterina ◽  
Rosa Sicari ◽  
An Yan ◽  
Walter Bernini ◽  
Daniela Giannessi ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Plasma Levels ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Random Sequence ◽  
Antiplatelet Agent ◽  
Antiplatelet Drug ◽  
Double Blind

SummaryIndobufen is an antiplatelet drug able to inhibit thromboxane production and cyclooxygenase-dependent platelet aggregation by a reversible inhibition of cyclooxygenase. Indobufen exists in two enantiomeric forms, of which only d-indobufen is active in vitro in inhibiting cyclooxygenase. In order to verify that also inhibition of platelet function is totally accounted for by d-indobufen, ten patients with proven coronary artery disease (8 male, 2 female, age, mean ± S.D., 58.7 ± 7.5 years) were given, in random sequence, both 100 mg d-indobufen and 200 mg dl-indobufen as single administrations in a double-blind crossover design study with a washout period between treatments of 72 h. In all patients thromboxane (TX) B2 generation after spontaneous clotting (at 0, 1, 2, 4, 6, 8, 12, 24 h), drug plasma levels (at the same times), platelet aggregation in response to ADP, adrenaline, arachidonic acid, collagen, PAF, and bleeding time (at 0, 2, 12 h) were evaluated after each treatment. Both treatments determined peak inhibition of TXB2 production at 2 h from administration, with no statistical difference between the two treatments (97 ±3% for both treatments). At 12 h inhibition was 87 ± 6% for d-indobufen and 88 ± 6% for dl-indobufen (p = NS). Inhibition of TXB2 production correlated significantly with plasma levels of the drugs. Maximum inhibitory effect on aggregation was seen in response to collagen 1.5 pg/ml (63 ± 44% for d-indobufen and 81 ± 22% for dl-indobufen) and arachidonic acid 0.5-2 mM (78 ± 34% for d-indobufen and 88 ± 24% for dl-indobufen) at 2 h after each administration. An effect of both treatments on platelet aggregation after 12 h was present only for adrenaline 2 μM (55 ± 41% for d-indobufen and 37 ± 54% for dl-indobufen), collagen 1.5 pg/ml (69 ± 30% for d-indobufen and 51 ± 61% for dl-indobufen), arachidonic acid 0.5-2 mM (56 ± 48% for d-indobufen and 35 ± 49% for dl-indobufen). The extent of inhibition of TX production and the extent of residual platelet aggregation were never significantly different between treatments. Bleeding time prolongation was similar in the two treatment groups without showing a pronounced and long lasting effect (from 7.0 ± 2.0 min to 10.0 ± 3.0 min at 2 h and 8.0 ± 2.0 min at 12 h for d-indobufen; from 6.0 ±1.0 min to 8.5 ± 2.0 min at 2 h and 8.0 ± 1.0 min at 12 h for dl-indobufen). These results demonstrate that the biological activity of dl-indobufen as an antiplatelet agent in vivo is totally accounted for by d-indobufen.

SB 497115-GR, a Low Molecular Weight TPOR Agonist, Does Not Induce Platelet Activation or Enhance Agonist-Induced Platelet Aggregation in Vitro.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3888-3888 ◽  
Author(s):  
Joseph Erhardt ◽  
Connie L. Erickson-Miller ◽  
Peter Tapley
Keyword(s):  
Molecular Weight ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Light Transmittance ◽  
Low Molecular Weight ◽  
Small Molecular Weight ◽  
Healthy Human ◽  
Induced Aggregation ◽  
Orally Active

Abstract SB-497115-GR is a low molecular weight, orally active molecule that requires Tpo receptor (TpoR) expession for activity and activates JAK/STAT signalling in platelets. The ability of recombinant Tpo to enhance agonist-induced platelet aggregation is well-documented, thus this study was undertaken to compare the ability of rhTpo (150 ng/ml) and SB-497115 (0.01–10 uM) to affect platelet activation. Platelets were obtained from healthy human volunteers, following written informed consent, by standard venipuncture technique. Citrated whole blood was used directly in platelet activation and P-selectin assays within 15 minutes. Platelet aggregation was assessed by light transmittance aggregometry. Aggregation was induced by a submaximal concentration of adenosine diphosphate (ADP) (1.0 or 1.5 uM) in experiments examining synergy with rhTpo (150ng/mL) or SB-497115 (0.01–10 uM). For examination of potential inhibitory actions of SB-497115 on platelet function, aggregation was induced by ADP (3 uM), collagen (2 ug/mL), or the thrombin receptor activating peptide (TRAP; 20 uM). Pre-treatment of platelet samples with rhTpo, but not SB-497115, potentiated the effects of 1.0 or 1.5 uM ADP. No inhibitory effect on normal ADP, Collagen or TRAP-induced aggregation was seen with either SB-497115-GR or rhTpo. In experiments investigating the expression of platelet P-selectin, an early marker of platelet activation, platelets labeled with anti-CD62P antibody were analyzed by flow cytometry. Data was expressed as percent of platelets positive for CD62P within the defined platelet gate. Treatment with SB-497115 (0.1 – 10 uM) demonstrated no induction of platelet CD62P expression above background levels. In contrast, rhTpo produced a modest but significant and reproducible increase in the percent of platelets positive for CD62P. This study demonstrates that, in contrast to rhTpo, the orally active small molecular weight agonist of the Tpo receptor, SB-497115-GR, does not mimic the ability of rhTpo to enhance ADP-induced aggregation of platelets. SB-497115-GR also did not directly induce P-selection expression on human platelets. Finally, SB-497115 has no antagonistic effect on ADP-, TRAP-, or collagen-induced platelet aggregation. Thus, SB-497115 is differentiated from rhTpo with respect to platelet activation.

In vitro Effects of Aprosulate sodium, a Novel Anticoagulant, On Platelet Activation: Possible Mechanism for Antiplatelet Action

1996 ◽  
Vol 76 (05) ◽  
pp. 786-790 ◽  
Author(s):  
Atsuhiro Sugidachi ◽  
Norbert Breiter ◽  
Taketoshi Ogawa ◽  
Fumitoshi Asai ◽  
Hiroyuki Koike
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Anticoagulant Activity ◽  
Acid Amide ◽  
Human Platelets ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Free System ◽  
Induced Aggregation

SummaryAprosulate sodium, a bis-lactobionic acid amide derivative, is a novel synthetic polyanion with potent anticoagulant activities. In the present study, the effects of aprosulate on platelet aggregation were investigated in a plasma-free system. Aprosulate inhibited thrombin (0.03-0.3 U/ml)-induced aggregation in rat washed platelets in a concentration-dependent manner, with an IC50 value of 0.38 Μg/ml. In contrast, aprosulate, at up to 10 Μg/ml, did not affect collagen (1 Μg/ml) - or ADP (3 ΜM)-induced aggregation. In fura 2-loaded platelets, aprosulate (1-10 Μg/ml) inhibited intracellular Ca2+ mobilization induced by thrombin, but not that by ADP. Protamine, a highly basic protein, abolished aprosulate-mediated inhibition of thrombin-induced platelet aggregation, suggesting that the observed inhibition is primarily due to the negative charge contained on the aprosulate molecule. In human platelets, aprosulate inhibited thrombin-induced aggregation, but failed to inhibit platelet aggregation induced by SFLLRN, a synthetic tethered ligand of a thrombin receptor. Antiplatelet profiles of aprosulate were largely similar to those of heparin, although heparin inhibited both thrombin- and collagen-induced aggregation. These in vitro studies indicate that aprosulate is capable of inhibiting thrombin-induced platelet activation and that this effect is independent of its anticoagulant activity. These results suggest that the polyanionic feature of aprosulate plays an essential role in promoting its antiplatelet activities, and that a plausible mechanism to explain the observed inhibition conferred by this agent, would be one which involves blocking the platelet-thrombin interaction.

In Vitro and in Vivo Functions of Thrombin-Treated Platelets

1976 ◽  
Vol 35 (01) ◽  
pp. 151-166 ◽  
Author(s):  
Hans-Joachim Reimers ◽  
Raelene L. Kinlough-Rathbone ◽  
Jean-Pierre Cazenave ◽  
Andrew F. Senyi ◽  
Jack Hirsh ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Untreated Control ◽  
Bleeding Time ◽  
Adenine Nucleotides ◽  
Rabbit Aorta ◽  
Creatine Phosphate ◽  
Irreversible Damage ◽  
Induced Aggregation

SummaryThrombin-induced platelet aggregation has been generally believed to be irreversible. However, thrombin-induced aggregation of washed platelets is reversible if fibrin formation is prevented or the fibrin which binds the platelets together is removed from the platelet aggregates. After treatment with high concentrations of thrombin (0.5 units/ml) single platelets can be recovered that have lost practically all of their releasable serotonin and adenine nucleotides. These platelets are able to aggregate upon addition of low concentrations of ADP in the presence of fibrinogen. They aggregate in response to the ionophore A23, 187 in the absence of added fibrinogen, whereas sodium arachidonate-induced aggregation requires added fibrinogen. Thrombin-treated platelets change their shape in response to collagen in the absence of fibrinogen, and will aggregate upon the addition of collagen providing fibrinogen is present. This response to collagen can be blocked with aspirin but not with a mixture of creatine phosphate/creatine phosphokinase. Upon a second exposure to thrombin, thrombin-pretreated platelets do not change their shape and do not undergo aggregation. Thrombin-pretreated platelets will not retract a thrombin-induced fibrin clot unless ADP, sodium arachidonate, the ionophore A23, 187 or collagen are added together with thrombin.The ability of thrombin-treated platelets to adhere to the exposed subendothelial surface of the rabbit aorta is reduced, compared with untreated control platelets. The thrombin-treated platelets shorten the bleeding time of thrombocytopenic rabbits. However, they are not as effective in shortening the bleeding time as normal control platelets. When injected into rabbits with a normal platelet count, the thrombin-treated platelets that circulate after infusion survive for the same length of time as untreated control platelets. These findings indicate that thrombin-induced platelet aggregation with extensive release of granule constituents is not irreversible and that thrombin treatment does not cause irreversible damage of all platelets that would lead to their immediate elimination from the circulation. Furthermore, these platelets can still be haemostatically effective. It is conceivable that platelets that have lost their amine storage granule contents during a release reaction in vivo, such as may occur in certain cases of intravascular coagulation and repeated episodes of thrombosis, may be found in the circulation of man.

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.

Reversible Inhibition of Human Platelet Activation by Hypothermia In Vivo and In Vitro

1994 ◽  
Vol 71 (05) ◽  
pp. 633-640 ◽  
Author(s):  
Alan D Michelson ◽  
Hollace MacGregor ◽  
Marc R Barnard ◽  
Anita S Kestin ◽  
Michael J Rohrer ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Whole Blood ◽  
Peripheral Blood ◽  
Bleeding Time ◽  
Human Platelet ◽  
Platelet Surface ◽  
Shed Blood

SummaryA hypothermia-induced hemorrhagic diathesis is associated with cardiopulmonary bypass, major surgery, and multiple trauma, but its pathophysiological basis is not well understood. We examined the hypothesis that hypothermia reversibly inhibits human platelet activation in vitro and in vivo. Platelet activation was studied in normal volunteers by whole blood flow cytometric analysis of modulation of platelet surface GMP-140 and the glycoprotein (GP) Ib-IX complex in: a) shed blood emerging from a standardized in vivo bleeding time wound; b) peripheral blood activated in vitro with either thrombin (in the presence of gly-pro-arg-pro, an inhibitor of fibrin polymerization) or the stable thromboxane (TX) A2 analogue U46619. Platelets in peripheral whole blood were activated at temperatures between 22° C and 37° C. the forearm skin temperature was maintained at temperatures between 22° C and 37° C prior to and during the bleeding time incision. Platelet aggregation was studied in shed blood by flow cytometry and in peripheral blood by aggregometry. Generation of TXB 2 (the stable metabolite of TXA 2) was determined by radioimmunoassay. In vitro, hypothermia inhibited both thrombin- and U46619-induced upregulation of GMP-140, downregulation of the GPIb-IX complex, platelet aggregation, and TXB2 generation. These inhibitory effects of hypothermia were all completely reversed by rewarming the blood to 37° C. In vivo, platelet activation was inhibited by hypothermia as shown by 5 independent assays of shed blood: upregulation of GMP-140, downregulation of the GPIb-IX complex, platelet aggregate formation, TXB 2 ggeneration, and the bleeding time. In summary, by a combination of immunologic, biochemical, and functional assays, we demonstrate that hypothermia inhibits human platelet activation in whole blood in vitro and in vivo. Rewarming hypothermic blood completely reverses the activation defect. These results suggest that maintaining normothermia or rewarming a hypothermic bleeding patient may reduce the need for platelet transfusions.

scholarly journals Antiplatelet and Antithrombotic Effects of Isaridin E Isolated from the Marine-Derived Fungus via Downregulating the PI3K/Akt Signaling Pathway

Marine Drugs ◽  
2021 ◽  
Vol 20 (1) ◽  
pp. 23
Author(s):  
Ni Pan ◽  
Zi-Cheng Li ◽  
Zhi-Hong Li ◽  
Sen-Hua Chen ◽  
Ming-Hua Jiang ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Signaling Pathway ◽  
Platelet Activation ◽  
Bleeding Time ◽  
Akt Signaling ◽  
Akt Signaling Pathway ◽  
Risk Of Bleeding ◽  
Antithrombotic Effects

Isaridin E, a cyclodepsipeptide isolated from the marine-derived fungus Amphichorda felina (syn. Beauveria felina) SYSU-MS7908, has been demonstrated to possess anti-inflammatory and insecticidal activities. Here, we first found that isaridin E concentration-dependently inhibited ADP-induced platelet aggregation, activation, and secretion in vitro, but did not affect collagen- or thrombin-induced platelet aggregation. Furthermore, isaridin E dose-dependently reduced thrombosis formation in an FeCl3-induced mouse carotid model without increasing the bleeding time. Mechanistically, isaridin E significantly decreased the ADP-mediated phosphorylation of PI3K and Akt. In conclusion, these results suggest that isaridin E exerts potent antithrombotic effects in vivo without increasing the risk of bleeding, which may be due to its important role in inhibiting ADP-induced platelet activation, secretion and aggregation via the PI3K/Akt pathways.

IMPAIREMENT OF PRIMARY HAEMOSTASIS BY LMW-HEPARINS

1987 ◽  
Author(s):  
A Borowska ◽  
D Lauri ◽  
A Maggi ◽  
E Dejana ◽  
G de Gaetano ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Anticoagulant Activity ◽  
Experimental Studies ◽  
Male Rats ◽  
Bleeding Complications ◽  
Low Molecular Weight ◽  
Bleeding Events

Low molecular weight (LMW) heparlns have been developed with the aim of reducing anticoagulant activity thereby minimizing the bleeding complications of conventional heparin. Unexpectedly, bleeding events were reported during treatment with some LMW-heparins, in clinical and experimental studies. We studied the effect of four different LMW-heparlns on primary haemostasis In male rats (CD COBS, Charles River) after l.v. administration of 0.75 mg/kg b.w. of the drugs. LMW heparin A was devoid of any activity on an experimental model of “template” bleeding time in rats (110.6±5.9 sec versus 108.7±4.1 control values) whereas LMW-heparins B, C and D prolonged the bleeding time to a different extent (228.7±19.9, 161.5±6.4 and 161.7±8.6 respectively). Pretreatment of animals with aspirin (100 mg/kg b.w. per o.s). resulted In a significant potentiation of the “template” bleeding time. In vitro platelet aggregation Induced by collagen (20 μg/ml) or by collagen in combination with ADP (5-10 μM) was strongly inhibited by LMW-heparln B, while LMW-heparln A showed no effect. LMW-heparins C and D exerted an Intermediate level of Inhibition of platelet aggregation. The same pattern of aggregating response was found when LMW-heparins A and B were given i.v. to rats (0.75 mg/kg b.w.) and platelet aggregation was studied “ex vivo” 15 min after drug administration.These data may help explain the impairment of primary haemostasis associated with some LMW-heparin preparations.

scholarly journals AN IMPORTANT STIMULATORY ROLE FOR THE cGMP-DEPENDENT PROTEIN KINASE II IN PLATELET ACTIVATION, IN VIVO THROMBOSIS AND HAEMOSTASIS

2020 ◽  
Author(s):  
Zhenyu Li ◽  
Ying Liang ◽  
can wang ◽  
Guoying Zhang ◽  
Jens Schlossmann ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Bleeding Time ◽  
Thrombus Formation ◽  
Atp Release ◽  
Downstream Signaling ◽  
Dependent Protein ◽  
Deficient Mice

Background and Purpose: The intracellular second messenger cGMP mediates signals by activating two types of cGMP-dependent protein kinases (PKG), PKG I and PKG II, differentially expressed in different cells. In platelets, cGMP mediates biphasic signals that stimulate and inhibit platelet activation, and the downstream signaling of cGMP is mediated by PKG I, the only PKG known to be expressed in platelets. However, functional defects of PKG I knockout platelets did not fully explain the roles of cGMP and the effect of PKG inhibitors on platelet activation. Experimental Approach: To determine if PKG II is present in platelets and plays a role in platelet activation, we performed RT-PCR and isolation of PKG II protein using cGMP-conjugated beads. We further determined platelet aggregation and ATP release in vitro, and FeCl3-injured carotid artery thrombosis as well as tail bleeding time in vivo. Key Results: PKG II is expressed in platelets and plays an important role in selectively stimulating platelet activation but not in the negative regulatory role of cGMP. Collagen-induced platelet aggregation and ATP secretion were reduced in PKG II-deficient mice but not PKG I-deficient mice. In contrast, low-dose thrombin-induced platelet activation depended on PKG I but not PKG II. Tail bleeding time and FeCl3-induced artery thrombus formation were significantly prolonged in PKG II knockout mice. Conclusion and Implication: PKG II-mediated cGMP signals are important in platelet activation, thrombosis and haemostasis in vitro and in vivo.

Comparative Arterial Antithrombotic Activity of Clopidogrel and Acetyl Salicylic Acid in the Pig

1992 ◽  
Vol 68 (05) ◽  
pp. 500-505 ◽  
Author(s):  
Ch M Samama ◽  
Ph Bonnin ◽  
M Bonneau ◽  
G Pignaud ◽  
E Mazoyer ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Femoral Artery ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Flow Reduction ◽  
Cyclic Flow ◽  
Left Femoral Artery ◽  
Before And After ◽  
The Right ◽  
Induced Aggregation

SummaryWe investigated the comparative antithrombotic properties of clopidogrel, an analogue of ticlopidine, and aspirin, using the Folts' model on femoral arteries in 22 pigs. On each animal, clopidogrel or aspirin were used to treat the thrombotic process on the left femoral artery and to prevent this process on the right femoral artery. Sequentially: an injury and stenosis were carried out on the left femoral artery; the thrombotic process was monitored with a Doppler during a 30-min observation period for cyclic flow reductions or permanent cessation of flow; after the first cyclic flow reduction occurred, clopidogrel (5 mg kg-1) or aspirin (2.5, 5, 100 mg kg-1) were injected intravenously; if cyclic flow reductions were abolished, epinephrine (0.4 µg kg-1 min-1) was injected to try to restore cyclic flow reductions and/or permanent cessation of flow; then injury and stenosis were applied on the right femoral artery. Before and after injection of clopidogrel or aspirin, ear immersion bleeding times and ex-vivo platelet aggregation were performed. Clopidogrel (n = 7) abolished cyclic flow reductions in all animals and epinephrine did not restore any cyclic flow reduction. On the right femoral artery, cyclic flow reductions were efficiently prevented, even for two injuries. Basal bleeding time (5 min 28) was lengthened (>15 min, 30 min after clopidogrel and remained prolonged even after 24 h). ADP-induced platelet aggregation was inhibited (more than 78%). Comparatively, aspirin had a moderate and no dose-dependent effect. Aspirin 2.5 mg kg-1 (n = 6) abolished cyclic flow reductions in 2 animals, CFR reoccurred spontaneously in one animal and epinephrine restored it in a second animal. Aspirin 5 mg kg-1 (n = 6) abolished cyclic flow reductions in only 3 animals and epinephrine always restored it. Aspirin 100 mg kg-1 (n = 3) was unable to abolish cyclic flow reductions. On the right femoral artery, aspirin did not significantly prevent cyclic flow reductions which occurred in all animals after one (n = 14) or two injuries (n = 1), except for one animal. Basal bleeding time was lengthened but it shortened rapidly, reaching its basal value after 24 h. ADP-induced aggregation was not significantly inhibited, whereas arachidonic acid induced aggregation was always inhibited. Clopidogrel appears as a more potent antithrombotic drug than aspirin in this model, in treating and preventing spontaneous or epinephrine-induced cyclic flow reductions and lengthening bleeding time.

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