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.

scholarly journals Release of arachidonic acid from human platelets. A key role for the potentiation of platelet aggregability in normal subjects as well as in those with nephrotic syndrome

Blood ◽  
1978 ◽  
Vol 52 (5) ◽  
pp. 969-977 ◽  
Author(s):  
N Yoshida ◽  
N Aoki
Keyword(s):  
Arachidonic Acid ◽  
Nephrotic Syndrome ◽  
Platelet Aggregation ◽  
Normal Subjects ◽  
Human Albumin ◽  
Membrane Phospholipids ◽  
Platelet Aggregability ◽  
Induced Aggregation

Abstract Low (nonaggregating) concentrations of collagen that potentiate platelet aggregation did not induce the formation of measurable amount of malondialdehyde (MDA) but released small but significant amounts of radioactivity from 14C-arachidonic acid-labeled platelets. A major portion of the radioactive compounds released by nonaggregating concentrations of collagen existed as arachidonic acid and a minor part as thromboxane B2. The nephrotic syndrome enhances platelet aggregability, and this effect is abolished by correcting hypoalbuminemia in vitro and in vivo by the addition of albumin, which is the main carrier for free fatty acids, including arachidonic acid. Human albumin (fatty acid free) inhibited collagen-induced aggregation, MDA formation, and release of the radioactivity from 14C-arachidonic acid-labeled platelets in normals as well as in those with nephrotic syndrome. These data support our hypothesis that the main mechanism responsible for the potentiation of platelet aggregation is the release of arachidonic acid from platelet membrane phospholipids via the activation of phospholipase A2. Furthermore, enhanced platelet aggregation in the nephrotic syndrome was at least partly attributable to an increased availability of arachidonic acid released secondary to hypoalbuminemia. Albumin inhibits aggregation probably by binding to released arachidonic acid preventing arachidonic acid from being metabolized to potent aggregating substances, endoperoxides and thromboxane A2. The mechanism of release of arachidonic acid may play a key role in the potentiation of platelet aggregability in normals as well as in pathologic conditions such as the nephrotic syndrome.

scholarly journals Release of arachidonic acid from human platelets. A key role for the potentiation of platelet aggregability in normal subjects as well as in those with nephrotic syndrome

Blood ◽  
1978 ◽  
Vol 52 (5) ◽  
pp. 969-977
Author(s):  
N Yoshida ◽  
N Aoki
Keyword(s):  
Arachidonic Acid ◽  
Nephrotic Syndrome ◽  
Platelet Aggregation ◽  
Normal Subjects ◽  
Human Albumin ◽  
Membrane Phospholipids ◽  
Platelet Aggregability ◽  
Induced Aggregation

Low (nonaggregating) concentrations of collagen that potentiate platelet aggregation did not induce the formation of measurable amount of malondialdehyde (MDA) but released small but significant amounts of radioactivity from 14C-arachidonic acid-labeled platelets. A major portion of the radioactive compounds released by nonaggregating concentrations of collagen existed as arachidonic acid and a minor part as thromboxane B2. The nephrotic syndrome enhances platelet aggregability, and this effect is abolished by correcting hypoalbuminemia in vitro and in vivo by the addition of albumin, which is the main carrier for free fatty acids, including arachidonic acid. Human albumin (fatty acid free) inhibited collagen-induced aggregation, MDA formation, and release of the radioactivity from 14C-arachidonic acid-labeled platelets in normals as well as in those with nephrotic syndrome. These data support our hypothesis that the main mechanism responsible for the potentiation of platelet aggregation is the release of arachidonic acid from platelet membrane phospholipids via the activation of phospholipase A2. Furthermore, enhanced platelet aggregation in the nephrotic syndrome was at least partly attributable to an increased availability of arachidonic acid released secondary to hypoalbuminemia. Albumin inhibits aggregation probably by binding to released arachidonic acid preventing arachidonic acid from being metabolized to potent aggregating substances, endoperoxides and thromboxane A2. The mechanism of release of arachidonic acid may play a key role in the potentiation of platelet aggregability in normals as well as in pathologic conditions such as the nephrotic syndrome.

A Study of Intravascular Platelet Aggregation in the Rat

1979 ◽  
Author(s):  
G. G. Duncan ◽  
G. M. Smith
Keyword(s):  
Arachidonic Acid ◽  
Platelet Count ◽  
Platelet Aggregation ◽  
Thromboxane A2 ◽  
Adenosine Diphosphate ◽  
Residual Response ◽  
Induced Aggregation ◽  
Anaesthetized Rat

Intravascular platelet aggregation can be studied by measuring the fall in the circulating platelet count induced by aggregating agents in anaesthetized animals. The Technicon Auto-counter was modified and connected via a double cannula to an anaesthetized rat to give a continuous count of the number of circulating platelets (1). Adenosine diphosphate (ADP), Collagen, Arachidonic acid (AA) and 5-Hydroxytryptamine (5-HT) were given at 15 minute intervals over a period of 2-3 hours. Aspirin (10 mg/Kg IV ) and Indomethacin (1-8 mg/Kg IV) partially inhibited collagen-induced aggregation and Indomethacin (2 mg/Kg IV) completely inhibited AA-induced aggregation. Adenosine (0.25 mg/min) inhibited the ADP-induced aggregation but did not inhibit aggregation produced by collagen or the residual response to collagen that remains after the addition of indomethacin.Reproducible responses to ADP and collagen were obtained but responses to AA and 5-HT were not reliable. Collagen-induced aggregation is thought to be mediated by the liberation of ADP, 5-HT and the formation of prostaglandin (PG ) endoperoxides and thromboxane A2. This study has shown that collagen-induced aggregation is reduced by inhibition of PG synthesis but the involvement of ADP or 5-HT could not be shown.

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.

Aspirin Ingestion in Primary Thrombocythemia

1982 ◽  
Vol 48 (01) ◽  
pp. 072-075 ◽  
Author(s):  
Akira Hattori ◽  
Masayoshi Sanada ◽  
Reizo Nagayama ◽  
Akira Shibata ◽  
Minoru Okuma
Keyword(s):  
Single Dose ◽  
Arterial Thrombosis ◽  
Platelet Rich Plasma ◽  
Thromboxane A2 ◽  
Primary Thrombocythemia ◽  
Normal Humans ◽  
Spontaneous Platelet Aggregation ◽  
Induced Aggregation ◽  
Aspirin Ingestion

SummaryRecently Massotti et al. (14) and Patrono et al. (23) have proposed for antithrombotic therapy the use of small single dose of aspirin (ASA) every three or four days in order to inhibit thromboxane A2 production in the platelets but not to inhibit PGI2 production in the endothelium. Their data are theoretical and based on a small number of normal humans. We have examined the effect of a single ingestion of ASA (10 mg/kg) on spontaneous platelet aggregation (SPA) and collagen-induced aggregation (CA) in 11 patients with primary thrombocythemia using the original platelet-rich plasma. SPA and CA were positive in 8 out of 10 and in 11 out of 11 patients respectively before ASA ingestion. ASA abolished both types of aggregation in all patients at 12 h after the ingestion. But the recovery occurred in 1/11 in CA at 24 hr, in about half (3/8 SPA or 7/11 CA) of the patients at 48 hr, in 5/8 (SPA) and 10/11 (CA) at 72 hr and in 7/ 8 (SPA) and 11/11 (CA) at 96 hr. Since SPA and sometimes CA have been considered to be the parameters of the effect of ASA on hyperreactivity of the platelets in vivo, resulting in arterial thrombosis or insufficiency in these patients, our results suggest that daily or at least once per two days ingestion of ASA may be necessary in these patients. These results were discussed in relation to the platelet survivals (6.5–10 days) and the platelet cyclo-oxygenase or lipoxygenase activities (deficient in 3 patients for the former and in 2 for the latter) in our patients.

Abstract 33: Platelet 12-lipoxygenase is a Key Regulator of Platelet Reactivity and Thrombus Formation in vivo

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Reheman Adili ◽  
Katherine Mast ◽  
Theodore R Holman ◽  
Michael Holinstat
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Platelet Reactivity ◽  
Thrombus Formation ◽  
High Shear ◽  
Vessel Occlusion ◽  
12 Lipoxygenase ◽  
Induced Aggregation

Background: Platelet reactivity is required to maintain hemostasis, however high platelet reactivity leads to thrombus formation, myocardial infarction, and stroke. Platelet 12-lipoxygenase (12-LOX) has been demonstrated by our lab and others to regulate agonist-mediated platelet reactivity suggesting a role for 12-LOX in regulation of in vivo thrombosis. The ability to target 12-LOX in vivo has not been established to date. Therefore, we sought to determine if 12-LOX regulates platelet reactivity and thrombus formation in vivo using the selective 12-LOX inhibitor ML355 to determine whether platelet 12-LOX is an effective target for anti-platelet therapeutics. Methods: ML355 effects on human platelet function was assessed in vitro by platelet aggregometry, ex vivo by perfusion chamber, and in vivo by thrombus formation and vessel occlusion in small and large vessels in 12-LOX -/- , WT mice, and mice treated with ML355 via intravital microscopy using the FeCl 3 and laser injury models. Results: In in vitro platelet aggregation, ML355 dose-dependently inhibited agonist-induced aggregation. In ex vivo flow chamber assays, platelet adhesion and thrombus formation on collagen-coated surfaces at high shear was attenuated in both mouse and human whole blood after incubation with ML355. Further, platelet aggregation and thrombus growth in 12-LOX -/- mice were impaired in both laser and FeCl 3 -induced mesenteric, carotid artery and cremaster arteriole thrombosis models. Thrombi in 12-LOX -/- mice were unstable and frequently formed emboli, which resulted in impaired vessel occlusion or reopening. Additionally, thrombus formation and vessel occlusion was impaired in ML355 treated WT mice. Conclusions: The 12-LOX inhibitor ML355 inhibits platelet aggregation induced by a number of platelet agonists. Ex vivo high shear conditions in both mice and human was attenuated in the presence of ML355. Thrombus formation and vessel occlusion were impaired in mice deficient in 12-LOX. Finally, ML355 attenuates thrombus formation and prevents vessel occlusion in vivo . Our data strongly indicates 12-LOX is an important determinant of platelet reactivity and inhibition of platelet 12-LOX may represent a new target for anti-platelet therapeutics.

Thromboxane A2-Stimulated Human Platelet Aggregation Is Potentiated By Epinephrine Acting VIA Alpha Adrenergic Receptors

1981 ◽  
Author(s):  
G J Johnson ◽  
G H R Rao ◽  
J G White
Keyword(s):  
Platelet Aggregation ◽  
Adrenergic Receptors ◽  
Human Platelet ◽  
Thromboxane A2 ◽  
Human Platelets ◽  
Adrenergic Agents ◽  
Alpha Adrenergic Receptors ◽  
Human Platelet Aggregation ◽  
Induced Aggregation

Epinephrine (E) potentiates arachidonate (A)-induced aggregation of human platelets. A-insensitive dog platelets (AIP), that form thromboxane A2 (T) but do not aggregate when stirred with A alone, aggregate when exposed to E + A. Therefore, we studied the effect of E on T-stimu- lated human platelet aggregation. AIP stirred with A formed T which was confirmed by TLC. 1/100 to 1/200 volume of AIP was removed 30 sec. after A, and transferred to gel- filtered, aspirin-incubated human platelets. Recipient platelet aggregation was proportional to the volume of AIP transferred. The addition of the thromboxane synthetase inhibitor, Azo Analog I, abolished the aggregating activity of AIP. Transfer of an aliquot of AIP that was inadequate to aggregate human gel-filtered, aspirin-incubated platelets resulted in irreversible aggregation in the presence of ≥0.5nM E. E potentiated aggregation when added 3 min. before but not 3 min. after aliquot transfer. T-stimulated aggregation was abolished by the T-antagonist, 13 azapro- stenoic acid (APA), but E added after APA and before T restored aggregation. E potentiation of T-stimulated aggregation was abolished by prior exposure to equimolar yohimbine, dihydroergocryptine and phentolamine, agents that bind to alpha2 adrenergic receptors, but not by prazosin an alpha1 antagonist. Higher concentrations of E reversed the inhibitory effects of the alpha2 adrenergic agents. All of these agents in higher concentrations (1-100μM) also blocked aggregation induced by T alone. Therefore T-induced platelet aggregation is potentiated by E, in concentrations attained in vivo, by a mechanism linked to platelet alpha adrenergic receptors. Platelet alpha2 receptors have a close functional relationship to the postulated T receptor. E may initiate platelet aggregation in vivo when T is formed in quantities inadequate to alone induce aggregation.

Lu 23051, A New Potent Inhibitor Of Platelet Aggregation

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

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

Sign in / Sign up

Export Citation Format

Share Document