INHIBITION OF GUINEA-PIG PLATELET FUNCTION IN VIVO AND EX VIVO USING THE THROMBOXANE A2 ANTAGONISTS, AH23848 AND GR32191

1987 ◽  
Author(s):  
P J McCabe ◽  
L E Stratton ◽  
E J Hornby ◽  
M Foster
Keyword(s):  
Platelet Aggregation ◽  
Guinea Pig ◽  
Guinea Pigs ◽  
Ex Vivo ◽  
Thromboxane A2 ◽  
In Vivo Studies ◽  
Maximum Inhibition ◽  
Platelet Deposition ◽  
Oral Doses

The thromboxane A2 antagonist, GR32191 (Lumley et al., this meeting) was tested as an inhibitor of platelet aggregation in the guinea-pig and compared with another Tx-antagonist, AH23848 (Brittain et al, 1985). Guinea-pigs were dosed with AH23848 or GR32191 at 0.01-1.0mg/kg. At intervals, blood was taken and PRP was prepared for ex vivo aggregation studies. Collagen concentrations causing half maximal aggregation (IC50) were calculated for test and vehicle-dosed groups. Inhibition was expressed as a concentration ratio (IC50 test/IC50 vehicle). For in vivo studies, 111In-labelled platelets (12μCi, 200μl) were injected into anaesthetised guinea-pigs and 24 hrs later oral doses of AH23848 or GR32191 (0.01-1.0mg/kg) or indomethacin (5mg/kg) were given. After one hour, blood was taken for platelet and radioactivity counting. The carotid artery was exposed under anaesthesia and a current of 2mA was applied for 60 sec. After 90 min, 1cm of the damaged and contralateral carotid vessels were removed for gamma-counting. Inhibition of accumulation of platelets on the injured artery was measured by comparison with the undamaged contralateral artery. Numbers of platelets deposited were calculated from the radioactivity of each section of artery and the radioactivity and platelet count in the blood. Oral doses of AH23848 or GR32191 inhibited ex vivo platelet aggregation induced by collagen. Maximum inhibition occurred one hour after dosing, and was still present at 6 hours for AH23848 (l.Omg/kg) and GR32191 (0.3mg/kg). GR32191 and AH23848 were active in vivo causing inhibition of platelet deposition at doses of 0.01-lmg/kg. The maximum inhibition of deposition was 58% for AH23848 (0.1mg/kg) and 63% for GR32191 (0.1mg/kg), with 50% inhibition at 0.02mg/kg for both. Indomethacin (5mg/kg p.o.) caused maximum inhibition of 58% at 5mg/kg p.o. suggesting that this represents the total thromboxane involvement in platelet deposition. GR32191 and AH23848 are thromboxane A2 antagonists with antithrombotic activity after oral dosing to guinea-pigs.Brittain R.T. et al Circulation, 72, 1208-1218, 1985.

Ex Vivo Inhibition of Platelet Aggregation in Patients with Severe Limb Arteriopathy Treated with BAY U3405, a Specific IX A2 Receptor Antagonist

1994 ◽  
Vol 72 (05) ◽  
pp. 659-662 ◽  
Author(s):  
S Bellucci ◽  
W Kedra ◽  
H Groussin ◽  
N Jaillet ◽  
P Molho-Sabatier ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Randomized Study ◽  
In Vivo Studies ◽  
Walking Distance ◽  
Peripheral Blood Flow ◽  
Walking Ability ◽  
Double Blind ◽  
Platelet Factor

SummaryA double-blind, placebo-controlled randomized study with BAY U3405, a specific thromboxane A2 (TX A2) receptor blocker, was performed in patients suffering from severe stade II limb arteriopathy. BAY U3405 or placebo was administered in 16 patients at 20 mg four times a day (from day 1 to day 3). Hemostatic studies were done before therapy, and on day 2 and day 3 under therapy. On day 3, BAY U3405 was shown to induce a highly statistically significant decrease of the velocity and the intensity of the aggregations mediated by arachidonic acid (56 ± 37% for the velocity, 58 ± 26% for the intensity) or by U46619 endoperoxide analogue (36 ± 35% for the velocity, 37 ± 27% for the intensity). Similar results were already observed on day 2. By contrast, such a decrease was not noticed with ADP mediated platelet aggregation. Furthermore, plasma levels of betathrombo-globulin and platelet factor 4 remained unchanged. Peripheral hemodynamic parameters were also studied. The peripheral blood flow was measured using a Doppler ultrasound; the pain free walking distance and the total walking ability distance were determined under standardized conditions on a treadmill. These last two parameters show a trend to improvement which nevertheless was not statistically significant. All together these results encourage further in vivo studies using BAY U3405 or related compounds on a long-term administration.

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.

scholarly journals The Novel TRPA1 Antagonist BI01305834 Inhibits Ovalbumin-Induced Bronchoconstriction in Guinea Pigs

2020 ◽  
Author(s):  
Mariska van den Berg ◽  
Susan Nijboer - Brinksma ◽  
Sophie Bos ◽  
Maarten van den Berge ◽  
David Lamb ◽  
...  
Keyword(s):  
Pilot Study ◽  
Guinea Pig ◽  
Guinea Pigs ◽  
Ex Vivo ◽  
Optimal Dose ◽  
Pig Model ◽  
The Novel ◽  
Airway Narrowing ◽  
Guinea Pig Model

Abstract Background: We hypothesized that TRPA1 channels contribute to airway hyperresponsiveness (AHR) and inflammation in asthma. We evaluated the efficacy of the novel TRPA1 antagonist BI01305834 in a guinea pig model of asthma. Methods: First a pilot study was performed in a guinea pig model of allergic asthma to find the optimal dose of BI01305834. Next, the effect of BI01305834 on AHR to inhaled histamine after the early and late asthmatic reaction (EAR and LAR), magnitude of EAR and LAR and airway inflammation was assessed. Precision-cut lung slices and trachea strips were used to investigate the bronchoprotective and bronchodilating effect of BI01305834. Statistical evaluation of differences of in vivo data was performed using a Mann-Whitney U test or One-way nonparametric Kruskal-Wallis ANOVA, for ex vivo data One- or Two-way ANOVA was used, all with Dunnett’s post-hoc test where appropriate.Results: A dose of 1 mg/kg BI01305834 was selected based on AHR and exposure data in blood samples from the pilot study. In the subsequent study 1 mg/kg BI01305834 inhibited AHR after the EAR, and the development of EAR and LAR elicited by ovalbumin in ovalbumin-sensitized guinea pigs. BI01305834 did not inhibit allergen-induced total and differential cells in the lavage fluid and interleukin-13 gene expression in lung homogenates. Furthermore, BI01305834 was able to inhibit allergen and histamine-induced airway narrowing in guinea pig lung slices, without affecting histamine release, and reverse allergen-induced bronchoconstriction in guinea pig trachea strips.Conclusions: TRPA1 inhibition protects against AHR and the EAR and LAR in vivo and allergen and histamine-induced airway narrowing ex vivo, and reverses allergen-induced bronchoconstriction, independently of inflammation. This effect was partially dependent upon histamine, suggesting a neuronal and possible non-neuronal role for TRPA1 in allergen-induced bronchoconstriction.

Effect of Picotamide on Platelet Aggregation and on Thromboxane A2 Production In Vivo

1991 ◽  
Vol 65 (03) ◽  
pp. 312-316 ◽  
Author(s):  
P Minuz ◽  
C Lechi ◽  
E Arosio ◽  
P Guzzo ◽  
M Zannoni ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Single Dose ◽  
Platelet Aggregation ◽  
Urinary Excretion ◽  
Ex Vivo ◽  
Thromboxane A2 ◽  
Normal Subjects ◽  
Dose Aspirin ◽  
Induced Aggregation

SummaryEffects of picotamide (900 mg in 3 oral administrations for 7 days) on ex vivo and in vivo platelet T×A2 production and on platelet aggregation wpre evaluated in 8 patients with peripheral arteriopathy and in 8 normal subjects. Picotamide significantly reduced ADP-induced platelet aggregation, but had no effect on that induced by arachidonic acid or the thromboxane analogue U46619. Though ex vivo platelet T×A2 production (T×B2 concentration after arachidonic-acid-induced aggregation) was reduced from 946 ± 141 (mean ± SD) to 285 ± 91 ng/ml in controls and from 1515 ± 673 to 732 ± 420 ng/ml in patients with arteriopathy, there was no effect on urinary excretion of 2,3-dinor-T×B2 (in vivo indicator of platelet T×A2 production), or on in vivo PGI2 production (urinary excretion of 6-keto-PGF1α and 2,3-dinor-6-keto-PGF1α). In the same subjects, single-dose aspirin reduced ex vivo T×B2 production by at least 98% and 2,3-dinor-T×B2 excretion from 116.7 ± 61.4 to 32.6 ± 17.0 nglg creatinine in control subjects, and from 156.3 ± 66.1 to 59.1 ± 19.2 ng/g creatinine in patients with peripheral arteriopathy. Our data suggest that inhibition of platelet T×A2 production in vivo may not be picotamide’s main mechanism of action.

A Thromboxane Synthetase Inhibitor Which Prolongs Bleeding Time In The Rat At Oral Doses Which Fail To Inhibit Platelet Aggregation In Vivo Or Ex Vivo

1981 ◽  
Author(s):  
K D Butler ◽  
E D Maguire ◽  
A A Turnbull ◽  
R B Wallis ◽  
A M White
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Inhibit Platelet Aggregation ◽  
Thromboxane Synthetase ◽  
Oral Doses ◽  
Rat Tail ◽  
Platelet Thromboxane

The role of thromboxane A2 (TXA2) in haemostasis was investigated with the use of a selective inhibitor of platelet thromboxane synthetase used in conjunction with radioimmunoassay of thromboxane B2 (TXB2). N-Carboxyheptylimidazole is such an inhibitor having no effect on platelet cyclooxygenase. An oral dose of this substance (10 mg/kg) to rats resulted in 85% (P < 0.001) suppression of platelet TXB2 production induced by collagen ex vivo while the ED50 and maximum rate of platelet aggregation were unchanged. It also caused a prolongation of tail bleeding time from 153±13 to 284±22 secs (P < 0.01). The thrombocytopenia resulting from the Arthus reaction in rats was unchanged, and the prothrombin and activated partial thromboplastin coagulation times were not affected by either 10 or 30 mg/kg p.o. It is concluded that the role of TXA2 in prevention of rat tail bleeding is not as an activator of platelet aggregation or blood coagulation. It is more likely that TXA2 prevents bleeding via its potent vaso-constricting properties. In addition the increased bleeding time may be due to change in the equilibrium of other vasoactive prostanoids.

scholarly journals Author Correction: A novel ruthenium (II)-derived organometallic compound, TQ-6, potently inhibits platelet aggregation: Ex vivo and in vivo studies

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Chih-Hsuan Hsia ◽  
Marappan Velusamy ◽  
Joen-Rong Sheu ◽  
Themmila Khamrang ◽  
Thanasekaran Jayakumar ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Organometallic Compound ◽  
Ex Vivo ◽  
In Vivo Studies

In Vivo Inhibition of Acute Platelet-Dependent Thrombosis in a Baboon Model by BAY U3405, a Thromboxane A2-Receptor Antagonist

1993 ◽  
Vol 70 (04) ◽  
pp. 672-675 ◽  
Author(s):  
H F Kotzé ◽  
S Lamprecht ◽  
P N Badenhorst ◽  
V van Wyk ◽  
J P Roodt ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Receptor Antagonist ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Thromboxane A2 ◽  
Arterial Blood Flow ◽  
Scintillation Camera ◽  
Graft Material ◽  
Txa2 Receptor

SummaryBay U3405 is a thromboxane A2 (TxA2)-receptor antagonist that inhibits the binding of TxA2 to its target cells. The aim of this study was to determine if Bay U3405 could be used to inhibit arterial thrombosis. A thrombogenic de vice, consisting of uncrimped Dacron vascular graft material (0.5 cm2) built into the wall of silicone rubber tubing with 4 mm inside diameter, was exposed to native flowing blood under arterial blood flow conditions (100-140 ml/min) by interposing the devices as extension segments into permanent femoral arteriovenous shunts implanted in baboons. Thrombus formation was quantified in vivo by measuring the deposition of 111In-labelled platelets onto the graft material with a scintillation camera. In six baboons, a bolus injection of Bay U3405, calculated to attain an initial plasma concentration of 300 ng/ml, reduced the maximum thrombus formation measured over a 2 h study period. Platelet deposition was reduced by 33 ± 14% (SD) at 2 h as compared to control studies done in the same baboons. The accumulation of additional platelets onto a thrombus that was allowed to form for 1 h, was reduced by 58 ± 28% at 2 h. Ex vivo platelet aggregation in response to ADP, activated partial thromboplastin time (APTT), prothrombin time (PT), and thrombin time (TT) were not affected by the treatment. Ex vivo platelet aggregation in response to collagen was markedly inhibited for 2 h after treatment. The results demonstrated that selective blocking of the TxA2-receptor on platelets reduced platelet-dependent thrombus formation and the accumulation of additional platelets in a freshly formed thrombus. This may provide a viable approach for preventing excessive thrombus formation in patients undergoing arterial reconstructive surgery.

scholarly journals A novel ruthenium (II)-derived organometallic compound, TQ-6, potently inhibits platelet aggregation: Ex vivo and in vivo studies

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Chih-Hsuan Hsia ◽  
Marappan Velusamy ◽  
Joen-Rong Sheu ◽  
Themmila Khamrang ◽  
Thanasekaran Jayakumar ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Organometallic Compound ◽  
Ex Vivo ◽  
In Vivo Studies

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.

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