Inhibition of Thrombus Formation by Endothelin-1 in Canine Models of Arterial Thrombosis

1995 ◽  
Vol 74 (06) ◽  
pp. 1583-1590 ◽  
Author(s):  
Robert J Leadley ◽  
William R Humphrey ◽  
Laurence A Erickson ◽  
Ronald J Shebuski
Keyword(s):  
Coronary Artery ◽  
Arterial Thrombosis ◽  
Cell Injury ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Vascular Endothelial Cell ◽  
Protective Mechanism ◽  
Antithrombotic Effect ◽  
Canine Models

SummaryThe effect of enclothelin-l (ET-1) on thrombus formation in vivo was evaluated in two well-established canine models of coronary artery thrombosis. First, the possible antithrombotic effect of ET-1 was examined using the cyclic flow reduction (CFR) model of coronary artery stenosis, vascular endothelial cell and intimal smooth muscle cell injury, and periodic acute platelet thrombus formation. Using a rating system of 0 (no inhibition) to 3 (complete inhibition), ET-1 administration at 0.1, 0.5, and 1.0 μg/kg, i.v. bolus, produced scores of 1.0 ± 0.2 (n = 10), 1.8 ± 0.4 (n = 8), and 2.1 ± 0.3 (n = 7), respectively. ET-1 injection inhibited ex vivo platelet aggregation induced by ADP and U-46619 by 30-60%. When aspirin was administered at 5 mg/kg prior to ET-1 administration at 0.5 pg/kg, ET-1 produced a CFR rating of 2.7 ± 0.2 (n = 6). However, higher dose aspirin (30 mg/kg, i.v.) significantly inhibited the antithrombotic effect of ET-1 (0.5 ± 0.5, n = 4). The antithrombotic effect of ET-1 was also examined using an electrolytic injury model of arterial thrombosis. The time required to produce an occlusive thrombus during the experiments in which ET-1 was administered at 10 and 20 ng kg-1 min-1 was 77 ± 15 (p <0.08) and 105 ± 16 min (p <0.05), respectively, compared to 44 ± 5 min when vehicle was infused. Cardiovascular changes following occlusion were not significantly different between dogs given ET-1 and those given vehicle, suggesting that elevated plasma levels of ET-1 did not exacerbate the adverse effects of coronary occlusion. In addition, plasma ET-1 levels were elevated significantly after occlusion in the dogs given vehicle (from 7.4 to 12.4 pg/ml). Taken together, these data provide further evidence to support the notion that ET-1 release during ischemia may be involved in a protective mechanism that impedes thrombus formation in the stenosed coronary artery.

Antithrombotic Effects and Bleeding Time Prolongation with Synthetic Platelet GPIIb/llla Inhibitors in Animal Models of Platelet-Mediated Thrombosis

1994 ◽  
Vol 71 (01) ◽  
pp. 095-102 ◽  
Author(s):  
Désiré Collen ◽  
Hua Rong Lu ◽  
Jean-Marie Stassen ◽  
Ingrid Vreys ◽  
Tsunehiro Yasuda ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Bolus Injection ◽  
Cell Injury ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Femoral Vein ◽  
Thrombotic Occlusion ◽  
Antithrombotic Effects

SummaryCyclic Arg-Gly-Asp (RGD) containing synthetic peptides such as L-cysteine, N-(mercaptoacetyl)-D-tyrosyl-L-arginylglycyl-L-a-aspartyl-cyclic (1→5)-sulfide, 5-oxide (G4120) and acetyl-L-cysteinyl-L-asparaginyl-L-prolyl-L-arginyl-glycyl-L-α-aspartyl-[0-methyltyrosyl]-L-arginyl-L-cysteinamide, cyclic 1→9-sulfide (TP9201) bind with high affinity to the platelet GPIIb/IIIa receptor.The relationship between antithrombotic effect, ex vivo platelet aggregation and bleeding time prolongation with both agents was studied in hamsters with a standardized femoral vein endothelial cell injury predisposing to platelet-rich mural thrombosis, and in dogs with a carotid arterial eversion graft inserted in the femoral artery. Intravenous administration of G4120 in hamsters inhibited in vivo thrombus formation with a 50% inhibitory bolus dose (ID50) of approximately 20 μg/kg, ex vivo ADP-induccd platelet aggregation with ID50 of 10 μg/kg, and bolus injection of 1 mg/kg prolonged the bleeding time from 38 ± 9 to 1,100 ± 330 s. Administration of TP9201 in hamsters inhibited in vivo thrombus formation with ID50 of 30 μg/kg, ex vivo platelet aggregation with an ID50 of 50 μg/kg and bolus injection of 1 mg/kg did not prolong the template bleeding time. In the dog eversion graft model, infusion of 100 μg/kg of G4120 over 60 min did not fully inhibit platelet-mediated thrombotic occlusion but was associated with inhibition of ADP-induccd ex vivo platelet aggregation and with prolongation of the template bleeding time from 1.3 ± 0.4 to 12 ± 2 min. Infusion of 300 μg/kg of TP9201 over 60 min completely prevented thrombotic occlusion, inhibited ex vivo platelet aggregation, but was not associated with prolongation of the template bleeding time.TP9201, unlike G4120, inhibits in vivo platelet-mediated thrombus formation without associated prolongation of the template bleeding time.

Specific Pharmacological Targeting of the Syk Kinase Activity in Platelets: A Novel, Safe Anti-Thrombotic Strategy

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 409-409 ◽  
Author(s):  
Suzanne Delaney ◽  
Uma Sinha ◽  
Nisha Nanda ◽  
Yibing Yan ◽  
Anjali Pandey ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Arterial Thrombosis ◽  
Kinase Activity ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Wild Type ◽  
Primary Hemostasis ◽  
Syk Kinase ◽  
Perfusion Chamber

Abstract Studies of the Syk −/− mouse have implicated spleen tyrosine kinase (Syk), a signaling protein with both kinase and scaffolding activities, in platelet signaling following engagement of GPVI and αIIbβ3 by collagen and fibrinogen, respectively. The present study was designed to determine whether specific inhibition of the kinase activity of Syk, without targeting the Syk scaffolding function, affected in vivo arterial thrombosis. In preliminary experiments, blood from wild-type and Syk−/− mice was perfused through collagen-coated capillaries under arterial shear rates to study ex vivo thrombosis. While blood from wild-type mice formed robust thrombi (37±4.7 μm3/μm2), none was observed in Syk−/− mice. Thrombi intermediate in size (16±3.9 μm3/μm2) developed in Syk+/− mice. To achieve specific pharmacological targeting of the kinase activity of Syk, P142-76, a potent (IC50 = 4 nM) and selective Syk kinase inhibitor was utilized. P142-76 was screened against a broad panel of 139 purified kinases at 50 nM. While Syk kinase was inhibited by 92%, all other kinases retained more than 70% of their activity. In washed human platelets, P142-76 inhibited convulxin (CVX)-induced phosphorylation of LAT (linker for activation of T-cells; IC50 = 111 nM) and intracellular calcium increases (IC50 = 31 nM). The GPVI/Syk-specificity of P142-76 activity was confirmed by its inability to inhibit intracellular calcium increases induced by the PAR1 thrombin receptor agonist TRAP. P142-76 also inhibited CVX-induced aggregation of both human washed platelets (IC50 = 87 nM) and platelet-rich plasma (IC50 = 2.5 μM). Considering the controversial data in respect to the participation of GPVI in arterial thrombosis in murine models, the dependence of arterial thrombosis on Syk function was studied in vivo in pigs. Cross-species activity of P142-76 was confirmed in vitro (CVX-induced PRP aggregation IC50= 350 nM; 5 μM P142-76 completely inhibited thrombosis triggered by collagen in the perfusion chamber assay). At a plasma concentration which abolished ex vivo CVX-induced but not ADP-induced pig platelet aggregation, P142-76 significantly inhibited the deposition of [111In]-labeled platelets in a carotid artery crush swine thrombosis model, without compromising primary hemostasis. % aggregation Swine (n=3) Platelet Deposition % inhibition Plasma Conc (ng/ml) Bleed Time (min) Activated Clotting Time (sec) ADP (20 μM) CVX (250 ng/ml) Control Artery 0 0 3±0.9 133±22 100 100 Treated Artery 76±6.5 1343±304 3.5±0.3 130±13 100 0 To clarify further the contribution of the kinase activity of Syk to arterial thrombosis, effects of P142-76 on human blood were evaluated in real time in the collagen-coated perfusion chamber. Low concentrations of P142-76 (0.3 μM) affected thrombus stability, while increasing concentrations (1–5 μM) delayed and then completely inhibited thrombus formation. Furthermore, P142-76 destabilized pre-formed thrombi, indicating a critical role for Syk in conferring strength to platelet-platelet interactions, i.e. αIIbβ3-mediated cohesion. Our data indicate that the kinase activity of Syk acts in arterial thrombosis through at least two distinct mechanisms. First, Syk kinase confers stability to platelet-platelet interactions downstream of αIIbβ3. Second, it initiates thrombus formation on collagen surfaces. This dual activity of the kinase activity of Syk makes it a preferred target for inhibition of arterial thrombosis, as it does not compromise primary hemostasis.

Inhibition of the von Willebrand (VWF)–collagen interaction by an antihuman VWF monoclonal antibody results in abolition of in vivo arterial platelet thrombus formation in baboons

Blood ◽  
2002 ◽  
Vol 99 (10) ◽  
pp. 3623-3628 ◽  
Author(s):  
Dongmei Wu ◽  
Karen Vanhoorelbeke ◽  
Nancy Cauwenberghs ◽  
Muriel Meiring ◽  
Hilde Depraetere ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Arterial Thrombosis ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
High Shear ◽  
Pharmacologic Effect ◽  
Antithrombotic Efficacy ◽  
Von Willebrand

The interaction between collagen, von Willebrand factor (VWF), and glycoprotein Ib is the first step in hemostasis and thrombosis especially under high shear conditions. We studied the inhibition of the VWF-collagen interaction by using an antihuman VWF monoclonal antibody 82D6A3 to prevent arterial thrombosis in baboons to develop a new kind of antithrombotic strategy and determine for the first time experimental in vivo data concerning the importance of the collagen-VWF interaction. We used a modified Folts model to study the antithrombotic efficacy of 82D6A3, where cyclic flow reductions (CFRs) were measured in the femoral artery. Administering a dose of 100, 300, and 600 μg/kg resulted in a 58.3%, 100%, and 100% reduction in the CFRs, respectively. When 100 μg/kg 82D6A3 was infused into the baboons, 80% of VWF-A3 domain was occupied, corresponding to 30% to 36% ex vivo inhibition of VWF binding to collagen, with no prolongation of the bleeding time. The bleeding time was also not significantly prolonged when the CFRs were abolished at doses of 300 μg/kg and 600 μg/kg. At these doses 100% of VWF was occupied by the antibody and 100% ex vivo inhibition of the VWF-collagen binding was observed. 82D6A3 has a high affinity for VWF; after 48 hours still 68% VWF (300μg/kg) was occupied with a pharmacologic effect up to 5 hours after administration (80%-100% occupancy). In conclusion, these results clearly indicate that the VWF-collagen interaction is important in vivo in thrombosis under high shear conditions and thus might be a new target for preventing arterial thrombosis.

The Tick Protein Ir-Cpi Efficiently Delays Contact Pathway Induced Thrombin Generation and Displays In Vivo Antithrombotic Activity

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3336-3336
Author(s):  
Severine Robert ◽  
Yves Decrem ◽  
Géraldine Rath ◽  
Chantal Dessy ◽  
Olivier Feron ◽  
...  
Keyword(s):  
Arterial Thrombosis ◽  
Thrombin Generation ◽  
Thrombus Formation ◽  
Lag Time ◽  
Antithrombotic Effect ◽  
Contact Phase ◽  
Antithrombotic Activity ◽  
Thrombosis Model ◽  
Contact Pathway

Abstract Abstract 3336 Introduction: The search for new anticoagulants is a major challenge in medicine. Contact factors have never been considered as interesting targets for the development of new anticoagulant agents since they are not required for in vivo coagulation (i.e. deficiencies affecting these factors do not cause excessive bleeding). The discovery that FXI and FXII deficiency protects against thrombosis without causing spontaneous bleeding in mice makes FXII a unique and ideal target for drug design. We demonstrated in vitro that Ir-CPI, a 67 amino acids recombinant Kunitz-type protein from Ixodes ricinus, specifically interacted with activated human contact phase factors (FXIIa, FXIa, and kallikrein). Aims: The goal of this study was to investigate the potential anticoagulant and antithrombotic efficacy of Ir-CPI. Methods: The effects of Ir-CPI were investigated on the thrombin activity during the coagulation process in human plasma using the CAT method. Three different inducers were employed to specifically trigger the coagulation pathways and to generate thrombin. A standard concentration of 5 pM TF with 4 μM PL and 16.7 mM CaCl2 was used to activate the TF pathway whereas a lower TF concentration of 1 pM with 4 μM PL and 16.7 mM CaCl2 was selected for stimulating the TF pathway in combination with the contact phase pathway through a thrombin-mediated positive feedback. The contact phase pathway was also triggered alone by ellagic acid, PL and 16.7 mM CaCl2 (25-fold diluted APTT reagent Actin FS). The effect of Ir-CPI on venous thrombus formation was assessed using a rat thrombosis model induced by complete venous stasis in the posterior vena cava and FeCl3 topical application on the outer vessel wall. Results: When stimulating plasma coagulation trough the contact pathway, Ir-CPI caused a concentration-dependent prolongation of the lag time and the Tmax and a concentration-dependent decrease in the Cmax compared to the control curve (i.e. without inhibitor). When the coagulation cascade was triggered by the TF pathway (5 or 1 pM TF), only a slight concentration-dependent decrease of the Cmax and a concentration-dependent prolongation of the lag time and the Tmax were observed. For comparison purpose, the effects of the specific competitive FXIIa inhibitor corn trypsin inhibitor (CTI) were also investigated using the three same inducers than for Ir-CPI. For the contact pathway, a concentration-dependent decrease of the Cmax and a concentration-dependent prolongation of the lag time and the Tmax were found. When stimulating the TF pathway (5 or 1 pM TF), no modification of the thrombin generation curves was observed with the tested concentrations of CTI. When comparing the results of the two inhibitors acting trough the delay of the contact pathway, we found that Ir-CPI was about 30-fold more potent than CTI. We further evaluated the antithrombotic effect of Ir-CPI on a rat venous thrombosis model induced by endothelial damage and vessel ligation, close to the physiological venous thrombus formation in humans. We showed that Ir-CPI reduced thrombosis in a dose-dependent manner with an ED50 close to 65 μg/kg. A maximum effect starting from 0.5 mg/kg was observed with a mean reduction in the clot weight/body weight of 75 ± 7%. This antithrombotic effect of Ir-CPI was exclusively mediated through the inhibition of thrombin generation since it did not interference with collagen-induced platelet aggregation. This is the first time that an inhibitor of the coagulation contact phase was shown to protect against the formation of venous thrombi. The antithrombotic effect of Ir-CPI was also confirmed using other venous and arterial thrombosis models. We also showed that the effective antithrombotic dose of Ir-CPI in these tests did not promote bleeding or impair blood coagulation parameters. Conclusions: The present study demonstrated that Ir-CPI, a recombinant protein from the tick Ixodes ricinus targeting the contact factors (FXII, FXI and kallikrein), displayed an anticoagulant activity mainly through the delay of the contact pathway induced thrombin generation. This drug also exhibited an antithrombotic activity in our venous and arterial thrombosis model. This drug may thus provide an interesting and innovative therapeutic tool for the prevention and the treatment of thromboembolic diseases with a minimal risk of therapy-associated bleeding. Disclosures: No relevant conflicts of interest to declare.

Prolonged Inhibition of Acute Arterial Thrombosis by High Dosing of a Monoclonal Anti-platelet Glycoprotein IIb/IIIa Antibody in a Baboon Model

1995 ◽  
Vol 74 (02) ◽  
pp. 751-757 ◽  
Author(s):  
H F Kotzé ◽  
P N Badenhorst ◽  
S Lamprecht ◽  
M Meiring ◽  
V Van Wyk ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Thrombus Formation ◽  
Extended Period ◽  
Platelet Glycoprotein ◽  
High Dose ◽  
Graft Material ◽  
Antithrombotic Effect ◽  
Baboon Model ◽  
Long Acting

SummaryThe in vivo activity of MA-16N7C2, the first monoclonal antibody that contains an echistatin-like RGD-sequence and inhibits platelet glycoprotein (GP)IIb/IIIa function, was determined in baboons. A dosefinding study assessing haemostatic variables such as bleeding time and ex vivo platelet aggregation showed that doses of as low as 0.2-0.3 mg/kg resulted in a pronounced effect. The effects were dose-dependent and lasted for several days, implying that MA-16N7C2 is a potent and long-acting GPIIb/IIIa inhibitor. Following the initial studies, the antithrombotic effect of 0.1 and 0.3 mg/kg of the antibody, given as a bolus, was determined in a baboon model of platelet-dependent, arterial-type thrombus formation. In these studies, a thrombogenic device consisting of Dacron vascular graft material was inserted as extension segments into a permanent arteriovenous shunt. The results confirmed the potent and long-lasting antithrombotic effect of MA-16N7C2. Surprisingly, the antithrombotic effect was stronger 48 h after a dose of 0.3 mg/kg administration than on the day of treatment with 0.1 mg/kg, despite the fact that comparable numbers of GPIIb/IIIa receptors were occupied on resting platelets. We postulate that with the high dose of MA-16N7C2 and after an extended period, occupied GPIIb/IIIa may be internalised by the platelets. Upon platelet activation, these receptors become reexposed but arc unable to participate in thrombus formation. This is in contrast to unoccupied internal GPIIb/IIIa receptors early after a low dose of MA-16N7C2.

7E3 F(ab’)2, an Effective Antagonist of Rat αIIbβ3 and αvβ3, Blocks In Vivo Thrombus Formation and In Vitro Angiogenesis

2001 ◽  
Vol 85 (05) ◽  
pp. 896-902 ◽  
Author(s):  
Patricia Sassoli ◽  
Eva Emmell ◽  
Susan Tam ◽  
Mohit Trikha ◽  
Zhao Zhou ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Aortic Ring ◽  
Canine Models ◽  
Sprout Formation ◽  
Double Crush ◽  
In Vitro Angiogenesis

SummaryAbciximab (c7E3 Fab, ReoPro®) blocks GPIIb/IIIa and αvβ3 and inhibits thrombotic and proliferative events only in humans and non-human primates. The bivalent F(ab’)2 fragment is an effective anti-thrombotic agent in canine models. In the present study, 7E3 F(ab’)2 was also found to bind to rat GPIIb/IIIa (KD = 27 ± 4 g/mL) and αvβ3 (KD = 9 ± 8 μg/mL), to block in vitro rat platelet aggregation (IC50 = 16 ± 6 μg/mL), and to inhibit αvβ3-mediated microvessel sprout formation in a rat aortic ring assay. Following administration of 7E3 F(ab’)2 (4 mg/kg) to rats, platelet aggregation was completely blocked for up to 6 h and thrombus formation in response to a rat abdominal aorta double crush injury was prevented. Effective chronic dosing was achieved with 6 mg/kg daily I.P. injections. In vitro mixing experiments indicated that 7E3 F(ab’)2 redistributed to unlabeled platelets in 2 h. Ex vivo, 7E3 F(ab’)2 was detected on platelets for up to 4 days after a single 4-mg/kg injection. These data suggest that 7E3 F(ab’)2 may be a useful agent to study the effects of GPIIb/IIIa and αvβ3 blockade in rat models of thrombosis and vascular disease.

Antithrombotic potential of new direct thrombin inhibitors built on the azaphenylalanine scaffold in two rat venous thrombosis models

2005 ◽  
Vol 93 (03) ◽  
pp. 437-442 ◽  
Author(s):  
Mojca Stegnar ◽  
Gorazd Drevenšek ◽  
Metka Budihna ◽  
Mojca Božič ◽  
Anamarija Zega ◽  
...  
Keyword(s):  
Venous Thrombosis ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Subcutaneous Administration ◽  
Thrombin Inhibitors ◽  
Direct Thrombin Inhibitors ◽  
Bolus Administration ◽  
Antithrombotic Effect ◽  
Antithrombotic Effects

SummaryThe antithrombotic potential of new direct thrombin inhibitors built on the azaphenylalanine scaffold (LK-732, LK-639 and LK-731) and their amidoxime prodrugs (LK-658, LK-633 and LK-730) was studied in comparison to argatroban and nadroparin in two rat models of venous thrombosis, induced either by complete stasis combined with hypercoagulability (model 1) or by partial stasis combined with vessel injury (model 2). In initial experiments LK-732 was established as the most promising antithrombotic of the LK inhibitors and as such was further tested. In model 1, intravenous bolus administration of LK-732 produced a dose-dependent inhibition of thrombus formation with an ID50 value of 1.3 mg/kg. This ID50 value was approximately four times higher than the ID50 value of argatroban (0.3 mg/kg; p=0.011). However, in model 2, LK-732 and argatroban decreased thrombus weight by 50% at similar ID50 values (3.8 mg/kg vs 3.0 mg/kg, respectively; p=0.726). The ex vivo anticoagulant effect of LK-732 was substantially weaker compared to argatroban at doses that produced comparable antithrombotic effects. After subcutaneous administration, in vivo thrombus weight reduction of LK inhibitors (10 mg/kg) ranged between 22 to 48%. However, their oral antithrombotic effect at a dose of 30 mg/kg was rather low. LK amidoxime prodrugs failed to produce a substantial antithrombotic effect after subcutaneous (10 mg/ kg) as well as after oral administration (30 mg/kg). In conclusion, thrombin inhibitors built on the azaphenylalanine scaffold represent a new group of intravenously effective antithrombotics. However, optimisation of the oral antithrombotic effect of amid-oxime prodrug LK-658 of the lead inhibitor LK-732 is required for justifying further development of these inhibitors.

Prevention of Canine Coronary Artery Thrombosis with Echistatin, a Potent Inhibitor of Platelet Aggregation from the Venom of the Viper, Echis carmatus

1990 ◽  
Vol 64 (04) ◽  
pp. 576-581 ◽  
Author(s):  
Ronald J Shebuski ◽  
Denise R Ramjit ◽  
Gary R Sitko ◽  
Patricia K Lumma ◽  
Victor M Garsky
Keyword(s):  
Coronary Artery ◽  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Artery Thrombosis ◽  
Coronary Artery Thrombosis ◽  
Canine Coronary Artery

SummaryA model of acute, platelet-dependent canine coronary artery thrombosis was utilized to assess the antithrombotic effect of a synthetic, RGD-containing 49-residue protein termed echistatin. This protein is derived from the venom of the viper, Echis carinatus. In vitro, echistatin inhibited ADP (10 ΜM)-induced platelet aggregation with IC50 values in human and canine platelet-rich plasma of 101 ± 4 and 127 ± 32 nM, respectively. In vivo, in the dog, infusion of echistatin for 30 min at 20 pg kg−1 min−1 or 2.6 nM kg−1 min−1 resulted in total abolition of acute platelet-dependent coronary thrombus formation in all dogs tested (n = 5). Infusion of a lower dose (10 pg kg−1 min−1) was not effective in prevention of thrombus formation. Blood samples were taken before and after infusion of echistatin in order to determine ex vivo platelet aggregatory responses. Echistatin (20 pg kg−1 min−1, i.v.) attenuated ex vivo platelet aggregation elicited by ADP, U-46619 and collagen and increased bleeding time by 2.9 ± 0.5-fold over control. Thus, in the dog, echistatin is an effective antithrombotic agent inhibiting both platelet aggregation in vivo in the coronary artery as well as ex vivo with a concomitant increase in bleeding time. Furthermore, the effects of echistatin on platelet aggregation and bleeding time are reversible with restoration to control levels occurring 30-60 min after termination of the infusion.

Comparison of the Inhibitory Effects of the TXA2 Receptor Antagonist, Vapiprost, and Other Antiplatelet Drugs on Arterial Thrombosis in Rats: Possible Role of TXA2

1992 ◽  
Vol 68 (04) ◽  
pp. 460-463 ◽  
Author(s):  
Yoshiharu Takiguchi ◽  
Kouichirou Wada ◽  
Mitsuyoshi Nakashima
Keyword(s):  
Platelet Aggregation ◽  
Receptor Antagonist ◽  
Arterial Thrombosis ◽  
Ex Vivo ◽  
Antiplatelet Drugs ◽  
Dependent Manner ◽  
Antithrombotic Effect ◽  
Antiplatelet Effect ◽  
Antithrombotic Effects

SummaryThe antithrombotic effect of the thromboxane A2 receptor antagonist, vapiprost, was compared with those of other antiplatelet drugs using an arterial thrombosis model which utilized photochemical reaction in the rat femoral artery. Vapiprost prolonged the time required to occlude the artery with thrombus and inhibited collagen-induced rat platelet aggregation in whole blood ex vivo, in a dose-dependent manner. The potency ranking of antithrombotic effect was vapiprost > ketanserin (serotonin 5-HT2 receptor antagonist) >> ticlopidine (inhibitor of ADP-induced platelet aggregation) = dipyridamole (adenosine uptake inhibitor) >aspirin (cyclooxygenase inhibitor). On the other hand, the ranking of antiplatelet effect was ticlopidine ≥vapiprost ≥aspirin. Ketanserin and dipyridamole were ineffective. Relative to their antiplatelet effect, vapiprost and ketanserin had powerful antithrombotic effects. It is possible that the potent antithrombotic effects of vapiprost and ketanserin in vivo reflect the ability of these drugs to inhibit mediator-induced vascular contractions in addition to platelet aggregation. The results of the present study also suggest that TXA2 may play an important role in thrombogenesis in rats.

The Modification of Experimental Occlusive Arterial Thrombosis in the Rat by Malayan Pit Viper Venom

1968 ◽  
Vol 19 (01/02) ◽  
pp. 242-247 ◽  
Author(s):  
K. E Chan
Keyword(s):  
Arterial Thrombosis ◽  
Thrombus Formation ◽  
Arterial Occlusion ◽  
Control Group ◽  
Antithrombotic Effect ◽  
Daily Dose

SummaryThe effect of Malayan pit viper (Ancistrodon rhodostoma) venom on the fate of experimental arterial thrombosis was studied in rats. A suitable daily dose of venom (500 μg) was used to induce hypofibrinogenaemia in the treated rats for the greater part of each of three consecutive post-operative days.The treated animals showed a statistically significant overall reduction in the incidence of both red thrombus formation and thrombotic arterial occlusion when compared to a control group. This antithrombotic effect of the venom could be observed in the 7-day period following the cessation of the treatment.

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