ORALLY ADMINISTERED VITAMIN B PROLONGS THE BLEEDING TIME AND INHIBITS PLATELET AGGREGATION IN HUMAN VOLUNTEERS.

1987 ◽  
Author(s):  
A M Randi ◽  
E Sacchi ◽  
M Cattaneo
Keyword(s):  
Platelet Aggregation ◽  
Vitamin B6 ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Vitamin B ◽  
Thrombin Time ◽  
Fibrin Formation ◽  
Primary Hemostasis ◽  
Coagulation Tests

It is known that mM concentrations of vitamin B6 inhibit human platelet aggregation and fibrin formation in vitro. There are very few and controversial data on the ex vivo effects of vitamin B6 on hemostatic parameters. We evaluated the effects of oral administration of vitamin B6 on bleeding time (BT), fibrin formation, platelet aggregation (PA) and the release reaction (RR). Vitamin B6 300 mg/day p.o., was given to 18 healthy volunteers (8 M, 10 F, aged 23-35) for 8 days. BT was measured before the first dose (Baseline), 2 hr after the first (Day 1) and the last dose (Day 8). In 7 subjects BT was measured also 7 days after the suspension of the drug (Day 15). Before and 2 hr after the first dose, prothrombin time (PT), partial thromboplastin time (PTT), thrombin time (TT), PA and the RR induced by different concentrations of ADP, PAF-acether, collagen (coll), epinephrine (epi), arachidonate (AA) were studied. BT was significantly prolonged after vitamin B6 administration, and returned to baseline values 7 days after suspension of the drug. PA and the RR induced by 1 uM ADP, 1 ug/ml coll or 5 uM epi were significantly inhibited 2 hours after vitamin B6 administration. Vitamin B6, however, did not affect PA or the RR induced by 0.2-2 uM PAF-acether, 2 uM ADP, 1 mM AA, 2 ug/ml coll, nor did it affect PT, PTT or TT. These data show that orally administered vitamin B impairs primary hemostasis, but does not affect fibrin 6 formation, as measured with standard coagulation tests.

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.

scholarly journals Effects of Juglans regia Root Bark Extract on Platelet Aggregation, Bleeding Time, and Plasmatic Coagulation: In Vitro and Ex Vivo Experiments

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
A. Amirou ◽  
M. Bnouham ◽  
A. Legssyer ◽  
A. Ziyyat ◽  
M. Aziz ◽  
...  
Keyword(s):  
Cardiovascular Diseases ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Juglans Regia ◽  
Anticoagulant Effect ◽  
Bark Extract ◽  
Root Bark ◽  
Thrombin Time ◽  
Induced Aggregation

Platelets have an important role in thrombosis and haemostasis. Hyperactivity of the platelets has been associated with thromboembolic diseases and represents the main cause of complications of cardiovascular diseases. Crude aqueous extract (CAE) of Juglans regia root bark was evaluated for bleeding time, antiaggregant activity by using agonists, thrombin, ADP, collagen, or arachidonic acid (in vitro and ex vivo), and anticoagulant activity by measuring the clotting parameters: activated partial thromboplastin time, prothrombin time, thrombin time, and fibrinogen dosage (in vitro and ex vivo). The result of this study reported that the strongest antiaggregant effect of CAE in vitro was observed on the ADP-induced aggregation with inhibitions up to 90 %, while, in ex vivo experiments, the inhibition (more than 80 %) was observed with all agonists. Anticoagulant effect of CAE significantly prolonged the TT and decreased the fibrinogen level in vitro and ex vivo without interfering with APTT and PT. The bleeding time in mice and rats was significantly increased by CAE. The antiplatelet and anticoagulant effect observed in this study suggest that Juglans regia could have antithrombotic and/or thrombolytic activities and provide an alternative therapy against thrombotic complications related to cardiovascular diseases.

scholarly journals Synthesis and Thrombin, Factor Xa and U46619 Inhibitory Effects of Non-amidino and Amidino N2-Thiophenecarbonyl- and N2-Tosylanthranilamides

2017 ◽  
Author(s):  
Soo Hyun Lee ◽  
Wonhwa Lee ◽  
Nguyen Thi Ha ◽  
Il Soo Um ◽  
Jong-Sup Bae ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Factor Xa ◽  
Inhibitory Effects ◽  
Human Endothelial Cells ◽  
Antithrombotic Activity ◽  
Pharmacological Targets

Thrombin (factor IIa) and factor Xa (FXa) are key enzymes at the junction of the intrinsic and extrinsic coagulation pathways and are the most attractive pharmacological targets for the development of novel anticoagulants. Twenty non-amidino N2-thiophencarbonyl- and N2-tosyl anthranilamides 1-20 and six amidino N2-thiophencarbonyl- and N2-tosylanthranilamides 21-26 were synthesized and evaluated prothrombin time (PT) and activated partial thromboplastin time (aPTT) using human plasma at concentration 30 μg/mL in vitro. From these results, compounds 5, 9, and 21-23 were selected to study the further antithrombotic activity. The anticoagulant properties of 5, 9, and 21-23 significantly exhibited a concentration-dependent prolongation of in vitro PT and aPTT, in vivo bleeding time, and ex vivo clotting time. These compounds concentration-dependently inhibited the activities of thrombin and FXa and inhibited the generation of thrombin and FXa in human endothelial cells. In addition, data showed that 5, 9, and 21-23 significantly inhibited thrombin catalyzed fibrin polymerization and mouse platelet aggregation and inhibited platelet aggregation induced U46619 in vitro and ex vivo. N-(3'-Amidinophenyl)-2-((thiophen-2''-yl)carbonyl amino)benzamide (21) was most active.

scholarly journals The effects of fructose diphosphate on routine coagulation tests in vitro

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Tongqing Chen ◽  
Duan Chen ◽  
Lu Chen ◽  
Zhengxu Chen ◽  
Baolong Wang ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Blood Coagulation ◽  
Detection System ◽  
Coagulation System ◽  
Thrombin Time ◽  
Aggregation Rate ◽  
Coagulation Testing ◽  
Coagulation Tests ◽  
Routine Coagulation

AbstractTo evaluate the effects of fructose diphosphate (FDP) on routine coagulation tests in vitro, we added FDP into the mixed normal plasma to obtain the final concentration of 0, 1, 2, 3, 4, 5, 6, 10, 15, 20, 25, 30 and 35 mg/mL of drug. Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen (FBG) and thrombin time (TT) of samples were analyzed with blood coagulation analyzers from four different manufacturers(Sysmex, Stago, SEKISUI and Werfen) and their corresponding reagents, respectively. Before the experiment, we also observed whether there were significant differences in coagulation test results of different lots of reagents produced by each manufacturer. At the same time as the four routine clotting tests, the Sysmex blood coagulation analyzer and its proprietary analysis software were used to detect the change of maximum platelet aggregation rate in platelet-rich plasma after adding FDP (0, 1, 2, 3, 4, 5 and 6 mg/mL). The results of PT, aPTT and TT showed a FDP (0–35 mg/mL) concentration-dependent increase and a FBG concentration-dependent decrease. The degree of change (increase or decrease) varied depending on the assay system, with PT and aPTT being more affected by the Sysmex blood coagulation testing instrument reagent system and less affected by CEKISUI, TT less affected by CEKISUI and more affected by Stago, and FBG less affected by Stago and more affected by Sysmex. The results of PT, aPTT and TT were statistically positively correlated with their FDP concentrations, while FBG was negatively correlated. The correlation coefficients between FDP and the coagulation testing systems of Sysmex, Stago, Werfen and SEKISUI were 0.975, 0.988, 0.967, 0.986 for PT, and 0.993, 0.989, 0.990 and 0.962 for aPTT, 0.994, 0.960, 0.977 and 0.982 for TT, − 0.990, − 0.983, − 0.989 and − 0.954 for FBG, respectively. Different concentrations of FDP (0, 1, 2, 3, 4, 5 and 6 mg/mL) had different effects on the maximum aggregation rate of platelet induced by the agonists of adenosine diphosphate (ADP, 5 µmol/L), arachidonic acid (Ara, 1 mmol/L), collagen (Col, 2.5 µg/mL) and epinephrine (Epi,10 µmol/L), but the overall downward trend was consistent, that is, with the increase of FDP concentration, the platelet aggregation rate decreased significantly. Our experimental study demonstrated a possible effect of FDP on the assays of coagulation and Platelet aggregation, which may arise because the drug interferes with the coagulation and platelet aggregation detection system, or it may affect our in vivo coagulation system and Platelet aggregation function, the real mechanism of which remains to be further verified and studied.

Effects of Magnesium on Platelet Aggregation and Adhesion

1994 ◽  
Vol 72 (06) ◽  
pp. 912-918 ◽  
Author(s):  
M Gawaz ◽  
I Ott ◽  
A J Reininger ◽  
F-J Neumann
Keyword(s):  
Myocardial Infarction ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Platelet Adhesion ◽  
Bleeding Time ◽  
Magnesium Deficiency ◽  
Ex Vivo ◽  
Surface Expression ◽  
Activated Platelets

SummaryMagnesium deficiency and its association with platelet hyperreactivity has been well recognised in a variety of diseases including myocardial infarction, preeclampsia, and diabetes. In order to investigate potential effects of intravenous Mg2+ supplementation, platelet function was studied by measurements of in vitro bleeding time (BT) and of fibrinogen (Fg)-mediated aggregation of washed platelets. In addition, the effect of Mg2+ on platelet adhesion onto immobilised Fg, on Fg binding to activated platelets, and on surface expression of GMP-140 or GP53 was evaluated. Mg2+(4 mM) prolonged in vitro BT by 30% and inhibited Fg-mediated aggregation significantly, independent of the agonist used to initiate platelet aggregation (ADP, collagen, epinephrine, thrombin, phorbol ester). Adhesion of resting platelets to immobilised Fg was reduced by 50% in the presence of 2 mM Mg2+. Moreover, Mg2+ reduced Fg binding to ADP- or collagen-stimulated platelets as well as surface expression of GMP-140 with an IC50 of approximately 3 mM. Intravenous administration of Mg2+ to healthy volunteers inhibited both ADP-induced platelet aggregation (p <0.05) by 40% and binding of Fg or surface expression of GMP-140 by 30% (p <0.05). Thus, pharmacological concentrations of Mg2+ effectively inhibit platelet function in vitro and ex vivo.

Antithrombotic Effect of a Recombinant von Willebrand Factor, VCL, on Nitrogen Laser-Induced Thrombus Formation in Guinea Pig Mesenteric Arteries

1995 ◽  
Vol 73 (02) ◽  
pp. 318-323 ◽  
Author(s):  
K Azzam ◽  
L I Garfinkel ◽  
C Bal dit Sollier ◽  
M Cisse Thiam ◽  
L Drouet
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Mesenteric Arteries ◽  
Antithrombotic Effects ◽  
Von Willebrand ◽  
Willebrand Factor

SummaryTo assess the antithrombotic effectiveness of blocking the platelet glycoprotein (GP) Ib/IX receptor for von Willebrand factor (vWF), the antiaggregating and antithrombotic effects were studied in guinea pigs using a recombinant fragment of vWF, Leu 504-Lys 728 with a single intrachain disulfide bond linking residues Cys 509-Cys 695. The inhibitory effect of this peptide, named VCL, was tested in vitro on ristocetin- and botrocetin-induced platelet aggregation and compared to the ADP-induced platelet aggregation. In vivo, the antithrombotic effect of VCL was tested in a model of laser-injured mesentery small arteries and correlated to the ex vivo ristocetin-induced platelet aggregation. In this model of laser-induced thrombus formation, five mesenteric arteries were studied in each animal, and the number of recurrent thrombi during 15 min, the time to visualization and time to formation of first thrombus were recorded.In vitro, VCL totally abolished ristocetin- and botrocetin-induced platelet aggregation, but had no effect on ADP-induced platelet aggregation. Ex vivo, VCL (0.5 to 2 mg/kg) administered as a bolus i. v. injection inhibits ristocetin-induced platelet aggregation with a duration of action exceeding 1 h. The maximum inhibition was observed 5 min after injection of VCL and was dose related. The same doses of VCL had no significant effect on platelet count and bleeding time. In vivo, VCL (0.5 to 2 mg/kg) had no effect on the appearance of the thrombi formed but produced dose-dependent inhibition of the mean number of recurrent thrombi (the maximal effect was obtained at 5 min following i. v. injection of the highest dose: 0.8 ± 0.2 thrombi versus 4 ± 0.4 thrombi in controls). The three doses of VCL increased the time in which the first thrombus in a concentration-dependent manner was formed. However, the time to visualize the first thrombus was only prolonged in the higher dose-treated group.These in-vivo studies confirm that VCL induces immediate, potent, and transient antithrombotic effects. Most importantly, this inhibition was achieved without inducing thrombocytopenia nor prolongation of the bleeding time.

Parsley extract inhibits in vitro and ex vivo platelet aggregation and prolongs bleeding time in rats

2009 ◽  
Vol 125 (1) ◽  
pp. 170-174 ◽  
Author(s):  
Dounia Gadi ◽  
Mohamed Bnouham ◽  
Mohammed Aziz ◽  
Abderrahim Ziyyat ◽  
Abdelkhaleq Legssyer ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo

scholarly journals Drug Interactions of Newer Oral Anticoagulants Dabigatran, Rivaroxaban, and Apixaban with Routinely Used Nonanticoagulant/Antiplatelet Drugs

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4267-4267 ◽  
Author(s):  
Shermin Sayani ◽  
Omer Iqbal ◽  
Debra Hoppensteadt ◽  
Jawed Fareed
Keyword(s):  
Platelet Aggregation ◽  
Tranexamic Acid ◽  
Oral Anticoagulant ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Fixed Concentration ◽  
Anticoagulant Drugs ◽  
Rat Tail

Abstract Introduction: The newer non-vitamin K antagonist oral anticoagulant drugs (NOACs) such as dabigatran, apixaban and rivaroxaban are now commonly used for various indications in a large group of patients who are simultaneously managed with several other routinely used drugs. Given the lack of available information on the interaction of newer oral anticoagulant drugs (NOACs) with commonly used non-anticoagulants / anti-platelet drugs, it is important to recognize the impact of these interactions on the safety and efficacy of these agents. We hypothesized that some of the commonly used drugs may modulate the anticoagulant effects of NOACs. This study aims to determine the antiplatelet, anticoagulant, and bleeding effects of the NOACs at varying concentrations with and without routinely used drugs both in the in vivo and in vitro systems. Materials and Methods:Dabigatran (Boehringer Ingelheim, Ridgefield, CT), rivaroxaban (Janssen Pharmaceuticals, Inc., Titusville, NJ), and apixaban (Bristol-Myers Squibb Company, Princeton, NJ and Pfizer Inc., New York, NY); and such routinely used drugs as alendronate sodium, chondroitin sulfate, hydrocodone-acetaminophen, klonopin, penicillin, tacrolimus, tramadol chlorhydrate, and tranexamic acid were commercially obtained and supplemented in citrated plasma at projected therapeutic ranges. Such tests as PT, APTT, dRVVT, TT, Heptest, and Anti- Xa and anti-IIa tests were performed. Agonist induced platelet aggregation studies using ADP, AA, Collagen, Epinephrine, and Thrombin agonists were performed on the Platelet Aggregation Profiler- 8 (PAP-8) (Biodata corporation, Horsham, PA) with dabigatran, apixaban and rivaroxaban alone and with the routinely used drugs. For the in-vivo bleeding studies a model of rat tail transection was used, following ketamine and xylazine anesthesia, 6-8 weeks old male Sprague-Dawley rats weighing 250-300g (n=15) were used to perform the rat tail transection bleeding time using dabigatran alone and dabigatran followed by tranexamic acid. Blood was drawn by cardiac puncture for ex vivo analysis. The collected data from the bleeding and ex vivo studies were tabulated and statistically analyzed using ANOVA. Results: In the in vitro studies, all of the NOACs produced assay dependant anticoagulant and antiprotease effects. Rivaroxaban and apixaban did not exhibit any interactions at the projected therapeutic dosage range when combined with any of the routinely used drugs. However dabigatran at a fixed concentration of 1 µg/ml combined with the commonly used drugs at a fixed concentration of 0.1 µg /ml or 1 µg/ml produced augmented assay-dependent anticoagulant and antiprotease activity. The most pronounced interaction was noticed with tacrolimus (111% difference in PT, 231% difference in APTT, and 46% difference in anti-IIa assay), followed by tramadol (57% difference in PT and 54% difference in Anti-IIa assay). Platelet Aggregation studies revealed no modulation of antiplatelet effects (<10%) with the addition of the commonly used drugs and the NOACs. In the rat tail transection bleeding model, there was a significant difference (p=0.03, α=0.05) between the bleeding time with dabigatran (100 µg/kg) alone (13.1 ±1.5 minutes) intravenously compared to dabigatran with tranexamic acid (10 mg/kg) (10.3 ±1.8 minutes) in each study. Ex-vivo analysis showed a reduction in PT and Heptest assay responses with dabigatran and tranexamic acid by 38% and 80%, respectively, and minimal change (5%) in APTT. Conclusion: In contrast to rivaroxban and apixaban in vitro, dabigatran exhibited stronger interactions with the commonly used drugs and variable assay dependent augmentation of anticoagulant and antiprotease responses. Tacrolimus and tramadol showed the strongest interactions. Agonist induced platelet aggregation studies did not show any interactions. Interestingly, tranexamic acid reduced the anticoagulant effect of dabigatran in the in vivo and ex vivo studies. These results warrant a review of post-marketing surveillance on the reported bleeding in patients concomitantly treated with NOACs and the reported routinely used drugs. Furthermore, these observations underscore the need to screen other commonly used drugs and supplements for their potential interactions with NOACs. Disclosures No relevant conflicts of interest to declare.

The Effects of Two Synthetic Glycoprotein II b/III a Antagonists, Ro 43-8857 and L-700,462, on Platelet Aggregation and Bleeding in Guinea-Pigs and Dogs: Evidence that Ro 43-8857 Is Orally Active

1993 ◽  
Vol 70 (05) ◽  
pp. 838-847 ◽  
Author(s):  
Nigel S Cook ◽  
Oliver Bruttger ◽  
Charles Pally ◽  
Alex Hagenbach
Keyword(s):  
Platelet Aggregation ◽  
Guinea Pigs ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Human Platelets ◽  
Mesenteric Arteries ◽  
Duration Of Action ◽  
Orally Active

SummaryIn vitro platelet aggregation studies in whole blood were used to define the species-specificity profile of two synthetic GP-IIb/IIIa antagonists, Ro 43-8857 and L-700,462. Aggregation of rhesus monkey platelets was inhibited with a similar potency to human platelets, whereas both compounds were poor antagonists in mini-pig, rabbit or hamster blood. Compared to human platelets, Ro 43-8857 was 2-3-fold less active as an inhibitor of dog and guinea-pig platelet aggregation, whereas L-700,462 was, respectively, 4- and 14-fold less active in these species.In vivo investigations with these two compounds were performed in anesthetized guinea-pigs and conscious dogs, with bleeding times measured on small mesenteric arteries or on the inner jowl respectively. Ex vivo ADP-induced whole blood platelet aggregation was completely inhibited in guinea-pigs by Ro 43-8857 following intravenous administration of 0.1 mg/kg and intraduodenal administration of 3 mg/kg, with a duration of action exceeding 5 hours. Mesenteric bleeding times were prolonged by Ro 43-8857 only at doses causing supra-maximal inhibition of aggregation, suggesting these two effects could be partially dissociated. L-700,462 (3 mg/kg i. v.) was shorter acting than Ro 43-8857 in guinea-pigs (duration ~1 hour) and the antiaggregatory effect was accompanied by mesenteric bleeding time prolongations. In conscious dogs, ex vivo aggregation was inhibited to —80% by Ro 43-8857 (0.3 mg/kg i. v. or 10 mg/kg p. o.) and L-700,462 (1 mg/kg i.v.). However, bleeding time prolongations accompanied these anti-aggregatory effects with both compounds.In conclusion, we have shown clear differences between two synthetic GP-IIb/IIIa antagonists, both in terms of their species-specificity in vitro and in terms of their in vivo profile, and in particular the propensity to promote bleeding from mesenteric arteries in guinea-pigs. However, the ability of Ro 43-8857 to discriminate between anti-aggregatory and bleeding effects was not evident when the bleeding time measurements were performed on the dog jowl. This suggests that the species and/or vessels on which the bleeding time is performed, is also an important consideration when characterizing and comparing antiplatelet compounds, even with drugs acting via the same mechanism. These results are relevant for the future design of in vivo animal experiments to characterize this new class of compounds and in the interpretation of the data obtained to the clinical situation. The animal models described here are well suited for comparative studies of different GP-IIb/IIIa antagonists, providing information on in vivo potency, duration of action and effect-bioavailability following different routes of administration.Orally active GP-IIb/IIIa antagonists have not previously been described in the literature. The long duration of action and oral activity shown by Ro 43-8857 suggests a potential use of such compounds in arterial thrombotic disorders requiring chronic therapy.

Inhibition of Thrombosis by a Selective Fibrinogen Receptor Antagonist without Effect on Bleeding Time

1994 ◽  
Vol 72 (01) ◽  
pp. 119-124 ◽  
Author(s):  
Juerg F Tschopp ◽  
Curt Mazur ◽  
Kenneth Gould ◽  
Raymond Connolly ◽  
Michael D Pierschbacher
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Dependent Manner ◽  
Ic50 Values ◽  
Receptor Assays ◽  
Dose Dependent ◽  
Fibrinogen Deposition

SummaryMembrane glycoprotein αIIbβ3 on platelets plays a pivotal role in hemostasis by mediating RGD-(arginine-glycine-aspartic acid)-dependent platelet adhesion and aggregation. Antagonists of αIIbβ3 ligand binding function, such as antibodies, snake venom peptides, or synthetic RGD-containing peptides can completely inhibit platelet aggregation in vitro and cause significant prolongation of bleeding times when injected into experimental animals. The in vitro and in vivo properties of an αIIbβ3 specific RGD-containing peptide 2G (G(Ten)GHRGDLRCA) were compared to two non-specific RGD-containing peptides IN (G(Pen)GRGDTPCA) and 2H (GRGDSPDG). All three peptides have similar IC50 values in human patelet aggregation (14-22 μM) and ELISA-based μIIbβ3 receptor assays (0.2–0.3 αM) but show different inhibitory activity (IC50 values) in the αv㯂5 (2G = 10 μM; IN = 0.06 μM; 2H = 0.05 μM) and receptor assays (2G = 8.3 μM; IN = 0.06 μM; 2H = 0.04). The αIIbβ3 specific peptide 2G had no effect on monolayers of human saphenous vein endothelial cells while IN and 2H caused many cells to detach and contract. Peptides 2G and IN inhibited ADP-stimulated ex vivo platelet aggregation in dogs in a dose dependent manner. When complete inhibition (>90%) of ex vivo platelet aggregation was achieved with either a 10 mg/kg bolus followed by a 16mg/kg/h infusion of 2G or with a 15 mg/kg bolus and 24 mg/kg/h infusion of IN, peptide IN caused a dose-dependent increase of the template bleeding time, while peptide 2G had no effect, even at doses up to 15 mg/kg bolus followed by 24 mg/kg/h infusion. The in vivo properties of peptides 2G and 2H were also examined in a baboon ex vivo shunt model for their ability to block platelet uptake and fibrinogen deposition on small caliber GORE-TEX® grafts and for their effect on the hemostatic system. Systemic administration of peptide 2G at 10 mg/kg bolus followed by 10 mg/kg/h infusion (or at a 2-fold lower dose) abolished platelet uptake and fibrinogen deposition on the graft surface without affecting the hemostasis and template bleeding time of the animal. By contrast, peptide 2H caused a 3-4-fold increase in bleeding time at a dose of 10 mg/kg. The results suggest that efficacy and the effect of specific aIIbp3antagonists on bleeding time can be separated and that selective aIIbP3 receptor blockade may be an efficient and safe approach to improve the patency and the success rate pf small caliber vascular grafts and to treat unwanted platelet-dependent thromboses. While peptide 2G may represent a unique class of antithrombotic agent, the clinical use of this type of molecule would require a significant enhancement in potency.

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