The Effects of Platelet-Derived Contractile Agents on Human Digital Arteries

1984 ◽  
Vol 66 (4) ◽  
pp. 443-451 ◽  
Author(s):  
R. F. W. Moulds ◽  
V. Iwanov ◽  
R. L. Medcalf
Keyword(s):  
Platelet Aggregation ◽  
Blood Vessels ◽  
Human Blood ◽  
Coronary Spasm ◽  
Prostaglandin F2α ◽  
Therapeutic Benefit ◽  
Human Platelets ◽  
Contractile Responses ◽  
Transient Ischaemic Attacks ◽  
Thromboxane Synthetase

1. The contractile responses of spiral strips of human digital arteries to samples of a suspension of human platelets aggregated by thrombin have been studied at different time intervals after aggregation. 2. Platelets added to the arterial strips 1 min after aggregation of the platelets produced contractile responses which were significantly greater than those produced by corresponding platelets added 20 min after aggregation. 3. When platelets were aggregated in the presence of indomethacin or the thromboxane synthetase antagonist 1-benzylimidazole, contractile responses produced by the platelets 1 min after aggregation were significantly reduced. They were then not significantly different from those produced by addition of the aliquots 20 min after aggregation, which were unaffected. 4. Pretreatment of the arteries with the serotonin antagonist ketanserin nearly abolished the contractile responses produced by addition of the platelets 20 min after aggregation, and significantly reduced those produced by addition of the platelets 1 min after aggregation. 5. Ketanserin did not affect the contractile responses of the arteries to potassium chloride, prostaglandin F2α, or the endoperoxide analogue U-46619, but antagonized the contractile effects of exogenous serotonin. 6. Combination of pretreatment of the arteries with ketanserin and aggregation of the platelets in indomethacin or 1-benzylimidazole virtually abolished contractile responses to platelets added both 1 min and 20 min after aggregation. 7. Tensions developed to different dilutions of platelets added 1 min after aggregation to arteries pretreated with ketanserin were not significantly different from those obtained to the same dilutions added 20 min after aggregation to arteries not pretreated with ketanserin. 8. It is concluded that there are two components to the contractile responses of human blood vessels produced by the aggregation of human platelets. One is labile, not produced when aggregation occurs in indomethacin or 1-benzylimidazole and is probably produced by thromboxane A2. The other is stable, markedly reduced by ketanserin, and probably produced by serotonin. Each of the components makes an approximately equal contribution to the contractures of human blood vessels produced by platelet aggregation. 9. It is also concluded that serotonin antagonists, in combination with a thromboxane synthetase inhibitor, may be of therapeutic benefit in clinical syndromes possibly mediated by platelet aggregation, such as cerebral transient ischaemic attacks and coronary spasm.

scholarly journals Survival and recovery of human platelets stored for five days in a non- plasma medium

Blood ◽  
1986 ◽  
Vol 67 (3) ◽  
pp. 672-675 ◽  
Author(s):  
GA Adams ◽  
SD Swenson ◽  
G Rock
Keyword(s):  
Platelet Aggregation ◽  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Plasma Medium ◽  
Release Reaction ◽  
In Vivo Recovery ◽  
Human Blood Platelets

Abstract Human blood platelets were stored for five days as concentrates in 60 mL of: (a) plasma; (b) non-plasma medium with anticoagulant; and (c) non-plasma medium without anticoagulant. All preparations were equally functional when tested for platelet aggregation and release reaction in response to single agonist or synergistic pairs of agonists in vitro. Platelets stored in non-plasma medium with anti-coagulant had lower kallikrein, fibrino(gen)peptide A, lactate, and beta-thromboglobulin than did plasma controls after five days. In vivo recovery and survival of platelets stored in non-plasma medium with anticoagulant were 51.2% +/- 4.3% and 8.7 +/- 0.3 days, respectively, which were not statistically different from plasma controls of 39.2% +/- 4.9% and 7.2 +/- 0.8 days, respectively. It is concluded that platelets can be stored for five days in a non-plasma medium and still have good in vivo recoveries and survivals.

Platelet Function in Alcoholics Treated with Disulfiram

1996 ◽  
Vol 2 (1) ◽  
pp. 51-54
Author(s):  
Maria Luigia Randi ◽  
Ilia Zanella ◽  
Piero Pujatti ◽  
Barbara Soini ◽  
Antonio Girolami
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Bleeding Time ◽  
Alcohol Intoxication ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Thromboxane Synthetase ◽  
Group A ◽  
Group B ◽  
Normal Controls

Disulfiram is usually used in alcoholics as aversion therapy. It binds to various enzymes and pro teins in blood and in tissues. In particular, it inhibits the thromboxane synthetase in human platelets and, for this reason, it has been surmised that disulfiram has a possible effect on platelet function. So far, disulfiram failed to confirm this hypothesis in healthy volunteers. However, it appears able to decrease the threshold collagen concen tration for platelet aggregation. Our aim was to evaluate the effect of disulfiram on the platelet function of alco holics. In this study, 24 alcoholics, divided in group A (12 abstinent patients with disulfiram 200 mg/day), group B (12 abstinent patients without treatment), and 17 normal controls, are reported. Different tests were performed at time 0 (acute alcohol intoxication), time 2, and time 15 after the beginning of abstinence. A significant increase was observed in bleeding time (BT) of group B and in platelet count of both groups. No modification was seen in prothrombin time. In group A, a significant increase of platelet aggregation under adenosine diphosphate (ADP; 2 μ M) stimulus was observed. Whereas no difference was seen in platelet 5-hydroxytryptamine (5-HT), serum 5-HT increased significantly at time 15 in group A. We con clude that the increase in serum 5-HT was probably due to the inhibition of monoamine oxidase (MAO) promoted by disulfiram, followed by an activation of MAO induced by disulfiram.

scholarly journals Survival and recovery of human platelets stored for five days in a non- plasma medium

Blood ◽  
1986 ◽  
Vol 67 (3) ◽  
pp. 672-675 ◽  
Author(s):  
GA Adams ◽  
SD Swenson ◽  
G Rock
Keyword(s):  
Platelet Aggregation ◽  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Plasma Medium ◽  
Release Reaction ◽  
In Vivo Recovery ◽  
Human Blood Platelets

Human blood platelets were stored for five days as concentrates in 60 mL of: (a) plasma; (b) non-plasma medium with anticoagulant; and (c) non-plasma medium without anticoagulant. All preparations were equally functional when tested for platelet aggregation and release reaction in response to single agonist or synergistic pairs of agonists in vitro. Platelets stored in non-plasma medium with anti-coagulant had lower kallikrein, fibrino(gen)peptide A, lactate, and beta-thromboglobulin than did plasma controls after five days. In vivo recovery and survival of platelets stored in non-plasma medium with anticoagulant were 51.2% +/- 4.3% and 8.7 +/- 0.3 days, respectively, which were not statistically different from plasma controls of 39.2% +/- 4.9% and 7.2 +/- 0.8 days, respectively. It is concluded that platelets can be stored for five days in a non-plasma medium and still have good in vivo recoveries and survivals.

scholarly journals Induction of Aggregation of Human Blood Platelets by Ultraviolet Light: Action Spectrum and Structural Changes

Blood ◽  
1973 ◽  
Vol 42 (4) ◽  
pp. 551-555 ◽  
Author(s):  
J. C. G. Doery ◽  
R. C. Dickson ◽  
J. Hirsh
Keyword(s):  
Platelet Aggregation ◽  
Ultraviolet Light ◽  
Human Blood ◽  
Structural Changes ◽  
Blood Platelets ◽  
Action Spectrum ◽  
Human Platelets ◽  
Ultrastructural Changes ◽  
Maximal Response ◽  
Human Blood Platelets

Abstract Exposure of washed human platelets to ultraviolet light is followed by platelet aggregation. The effect occurs at wavelengths between 302 and 225 mµ with a maximal response at 248 mµ, and the effect is greatly enhanced by the addition of fibrinogen. Platelets exposed to ultraviolet light show ultrastructural changes which can be induced independently of aggregation if the addition of fibrinogen is omitted.

Selective Inhibition Of Thromboxane Synthesis By 1-(3-Hydroxy-1-Octenyl)-Imidazole And Its Nicotinic Ester In Human And Rat Platelets

1981 ◽  
Author(s):  
C Bonne ◽  
B Martin ◽  
D Sincholle ◽  
F Regnault
Keyword(s):  
Platelet Aggregation ◽  
Selective Inhibition ◽  
Rat Aorta ◽  
Human Platelets ◽  
Aorta Ring ◽  
Thromboxane Synthetase ◽  
Thrombotic Diseases ◽  
Induced Aggregation ◽  
Rat Platelets

Since Thromboxane A2 (T×A2) is considered to play an important role in platelet aggregation, attempts to develop selective inhibitors of T×A2- synthetase are being made. In this report the activity of 1-(3-hydroxy-1-octenyl)-imidazole, chlorhydrate (CBS612) and of its nicotinic ester, die hiorhydrat e (CBS63b) will be presented.The inhibitory activity was determined in isolated platelets from human and rat by radiochemical assay and in whole blood by radioimmunoassay of T×B2 and of PGE2 as a criteria of specificity. Human enzyme was more sensitive than the rat one’s (CBS634 : IC50 human = 0.7μM, IC50 rat = 10μM) and the two compounds were more active than imidazole in human platelets (IC50 : imidazole = 50μM, CBS612 = 2μM ; CBS631+ = 0.7μM). Collagen- induced aggregation was inhibited by the drugs at concentrations which suppressed T×B2 formation.The results of these experiments showed that CBS612 and CBS634 selectively inhibited thromboxane-synthetase since they increased the formation of PGE2. Besides, these compounds did not inhibit PGI2 release from rat aorta ring. The selectivity of the inhibition by the drugs was further shown by the absence of any effect on the first phase of ADP-induced platelet aggregation.These compounds seemed potentially interesting for the management of thrombotic diseases and for elucidating the role of Thromboxane in physiological and pathological processes.

In Vitro And In Vivo Effects Of An Inhibitor Of Thromboxane Synthetase

1981 ◽  
Author(s):  
G Defreyn ◽  
L O Carreras ◽  
S J Machin ◽  
J Vermylen ◽  
M Verstraete
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Cyclic Amp ◽  
Prostaglandin F2α ◽  
Test System ◽  
Controlled Study ◽  
Double Blind ◽  
Thromboxane Synthetase

UK-37,248, 4-(2-(lH-imidazol-l-yl)ethoxy)benzoic acid hydrochloride, completely inhibits platelet aggregation in plasma by low concentrations of arachidonic acid at 0.5 uM and thromboxane B2(TXB2) generation in washed platelets at 10 uM. In the latter test system the total amount of cyclooxygenase metabolites is unaltered, the decrease in TXB^ and hydroxyhepatadecatrienoic acid being compensated by an increase in prostaglandins E2 and F2α . Arachidonic acid challenged platelets pretreated with UK-37,248 do not accumulate cyclic AMP ; they however strongly stimulate the production of prostacyclin by aspirin pretreated cultured endothelial cells.In a double blind placebo controlled study ingestion of 200 mg of the compound resulted in a complete inhibition of arachidonic acid induced platelet aggregation, whereas the threshold concentration for irreversible platelet aggregation with ADP was unaltered. Serum TXB2 levels were markedly decreased from the normal pre-values (200-700 pg/ml) to low (60-80 pg/ml). Stimultaneous plasma 6-keto prostaglandin F2α , levels from citrate blood increased from 46 ± 23 pg/ml (mean ± SD) to 409 ± 185 pg/ml).It is concluded that a thromboxane synthetase inhibitor modifies cyclic endoperoxide metabolism in such a way that there is not only a decreased formation of pro-aggregatory thromboxane A2 but also an increased production of antiaggregatory prostacyclin. Thromboxane-synthetase inhibitors may be superior to aspirin as antithrombotic agents. The platelet function defect induced by UK-37,248 is only distinct from that in congenital thromboxane synthetase deficiency in that in the latter condition ADP aggregation always is reversible and arachidonic acid challenged platelets accumulate cyclic AMP (Defreyn et al, 1981). Probably UK-37,248, like imidazole itself, activates phosphodiesterase, thus abolishing part of its anti-aggregating effect.

Functional Characterization of PM6/13, a β3-specific (GPIIIa/CD61) Monoclonal Antibody that Shows Preferential Inhibition of Fibrinogen Binding over Fibronectin Binding to Activated Human Platelets

1998 ◽  
Vol 79 (01) ◽  
pp. 177-185 ◽  
Author(s):  
Ashia Siddiqua ◽  
Michael Wilkinson ◽  
Vijay Kakkar ◽  
Yatin Patel ◽  
Salman Rahman ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Functional Characterization ◽  
Human Platelets ◽  
Western Blots ◽  
Activated Platelets ◽  
Reducing Conditions ◽  
Fibronectin Binding

SummaryWe report the characterization of a monoclonal antibody (MAb) PM6/13 which recognises glycoprotein IIIa (GPIIIa) on platelet membranes and in functional studies inhibits platelet aggregation induced by all agonists examined. In platelet-rich plasma, inhibition of aggregation induced by ADP or low concentrations of collagen was accompanied by inhibition of 5-hydroxytryptamine secretion. EC50 values were 10 and 9 [H9262]g/ml antibody against ADP and collagen induced responses respectively. In washed platelets treated with the cyclooxygenase inhibitor, indomethacin, PM6/13 inhibited platelet aggregation induced by thrombin (0.2 U/ml), collagen (10 [H9262]g/ml) and U46619 (3 [H9262]M) with EC50 = 4, 8 and 4 [H9262]g/ml respectively, without affecting [14C]5-hydroxytryptamine secretion or [3H]arachidonate release in appropriately labelled cells. Studies in Fura 2-labelled platelets revealed that elevation of intracellular calcium by ADP, thrombin or U46619 was unaffected by PM6/13 suggesting that the epitope recognised by the antibody did not influence Ca2+ regulation. In agreement with the results from the platelet aggregation studies, PM6/13 was found to potently inhibit binding of 125I-fibrinogen to ADP activated platelets. Binding of this ligand was also inhibited by two other MAbs tested, namely SZ-21 (also to GPIIIa) and PM6/248 (to the GPIIb-IIIa complex). However when tested against binding of 125I-fibronectin to thrombin stimulated platelets, PM6/13 was ineffective in contrast with SZ-21 and PM6/248, that were both potent inhibitors. This suggested that the epitopes recognised by PM6/13 and SZ-21 on GPIIIa were distinct. Studies employing proteolytic dissection of 125I-labelled GPIIIa by trypsin followed by immunoprecipitation with PM6/13 and analysis by SDS-PAGE, revealed the presence of four fragments at 70, 55, 30 and 28 kDa. PM6/13 did not recognize any protein bands on Western blots performed under reducing conditions. However Western blotting analysis with PM6/13 under non-reducing conditions revealed strong detection of the parent GP IIIa molecule, of trypsin treated samples revealed recognition of an 80 kDa fragment at 1 min, faint recognition of a 60 kDa fragment at 60 min and no recognition of any product at 18 h treatment. Under similar conditions, SZ-21 recognized fragments at 80, 75 and 55 kDa with the 55kDa species persisting even after 18 h trypsin treatment. These studies confirm the epitopes recognised by PM6/13 and SZ-21 to be distinct and that PM6/13 represents a useful tool to differentiate the characteristics of fibrinogen and fibronectin binding to the GPIIb-IIIa complex on activated platelets.

Ticlopidine Facilitates the Deaggregation of Human Platelets Aggregated by Thrombin

1994 ◽  
Vol 71 (01) ◽  
pp. 091-094 ◽  
Author(s):  
M Cattaneo ◽  
B Akkawat ◽  
R L Kinlough-Rathbone ◽  
M A Packham ◽  
C Cimminiello ◽  
...  
Keyword(s):  
Cardiovascular Disease ◽  
Platelet Aggregation ◽  
Prostaglandin E1 ◽  
Human Platelet ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Before And After ◽  
Normal Human ◽  
Platelet Aggregates ◽  
Induced Aggregation

SummaryNormal human platelets aggregated by thrombin undergo the release reaction and are not readily deaggregated by the combination of inhibitors hirudin, prostaglandin E1 (PGE1) and chymotrypsin. Released adenosine diphosphate (ADP) plays an important role in the stabilization of thrombin-induced human platelet aggregates. Since ticlopidine inhibits the platelet responses to ADP, we studied thrombin-induced aggregation and deaggregation of 14C-serotonin-labeled platelets from 12 patients with cardiovascular disease before and 7 days after the oral administration of ticlopidine, 250 mg b.i.d. Before and after ticlopidine, platelets stimulated with 1 U/ml thrombin aggregated, released about 80–90% 14C-serotinin and did not deaggregate spontaneously within 5 min from stimulation. Before ticlopidine, hirudin (5× the activity of thrombin) and PGE1 (10 μmol/1) plus chymotrypsin (10 U/ml) or plasmin (0.06 U/ml), added at the peak of platelet aggregation, caused slight or no platelet deaggregation. After ticlopidine, the extent of platelet deaggregation caused by the same inhibitors was significantly greater than before ticlopidine. The addition of ADP (10 μmol/1) to platelet suspensions 5 s after thrombin did not prevent the deaggregation of ticlopidine-treated platelets. Thus, ticlopidine facilitates the deaggregation of thrombin-induced human platelet aggregates, most probably because it inhibits the effects of ADP on platelets.

The Effect of Red Blood Cells on the ADP-induced Aggregation of Human Platelets in Flow Through Tubes

1990 ◽  
Vol 63 (01) ◽  
pp. 112-121 ◽  
Author(s):  
David N Bell ◽  
Samira Spain ◽  
Harry L Goldsmith
Keyword(s):  
Platelet Aggregation ◽  
Shear Rate ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Platelet Rich Plasma ◽  
Mean Transit Time ◽  
White Blood Cells ◽  
Aggregate Size ◽  
Human Platelets ◽  
Induced Aggregation

SummaryThe effect of red blood cells, rbc, and shear rate on the ADPinduced aggregation of platelets in whole blood, WB, flowing through polyethylene tubing was studied using a previously described technique (1). Effluent WB was collected into 0.5% glutaraldehyde and the red blood cells removed by centrifugation through Percoll. At 23°C the rate of single platelet aggregtion was upt to 9× greater in WB than previously found in platelet-rich plasma (2) at mean tube shear rates Ḡ = 41.9,335, and 1,920 s−1, and at both 0.2 and 1.0 µM ADP. At 0.2 pM ADP, the rate of aggregation was greatest at Ḡ = 41.9 s−1 over the first 1.7 s mean transit time through the flow tube, t, but decreased steadily with time. At Ḡ ≥335 s−1 the rate of aggregation increased between t = 1.7 and 8.6 s; however, aggregate size decreased with increasing shear rate. At 1.0 µM ADP, the initial rate of single platelet aggregation was still highest at Ḡ = 41.9 s1 where large aggregates up to several millimeters in diameter containing rbc formed by t = 43 s. At this ADP concentration, aggregate size was still limited at Ḡ ≥335 s−1 but the rate of single platelet aggregation was markedly greater than at 0.2 pM ADP. By t = 43 s, no single platelets remained and rbc were not incorporated into aggregates. Although aggregate size increased slowly, large aggregates eventually formed. White blood cells were not significantly incorporated into aggregates at any shear rate or ADP concentration. Since the present technique did not induce platelet thromboxane A2 formation or cause cell lysis, these experiments provide evidence for a purely mechanical effect of rbc in augmenting platelet aggregation in WB.

Effects of a Monoclonal Antibody to Glycoprotein IIb/IIIa (P256) and of Enzymically Derived Fragments of P256 on Human Platelets

1991 ◽  
Vol 65 (04) ◽  
pp. 432-437 ◽  
Author(s):  
A W J Stuttle ◽  
M J Powling ◽  
J M Ritter ◽  
R M Hardisty
Keyword(s):  
Monoclonal Antibody ◽  
Flow Cytometry ◽  
Platelet Aggregation ◽  
Calcium Ions ◽  
Human Platelet ◽  
Human Platelets ◽  
In Vivo Detection ◽  
Fibrinogen Binding ◽  
Specific Antagonist

SummaryThe anti-platelet monoclonal antibody P256 is currently undergoing development for in vivo detection of thrombus. We have examined the actions of P256 and two fragments on human platelet function. P256, and its divalent fragment, caused aggregation at concentrations of 10−9−3 × 10−8 M. A monovalent fragment of P256 did not cause aggregation at concentrations up to 10−7 M. P256–induced platelet aggregation was dependent upon extracellular calcium ions as assessed by quin2 fluorescence. Indomethacin partially inhibited platelet aggregation and completely inhibited intracellular calcium mobilisation. Apyrase caused partial inhibition of aggregation. Aggregation induced by the divalent fragment was dependent upon fibrinogen and was inhibited by prostacyclin. Aggregation induced by the whole antibody was only partially dependent upon fibrinogen, but was also inhibited by prostacyclin. P256 whole antibody was shown, by flow cytometry, to induce fibrinogen binding to indomethacin treated platelets. Monovalent P256 was shown to be a specific antagonist for aggregation induced by the divalent forms. In–111–labelled monovalent fragment bound to gel-filtered platelets in a saturable and displaceable manner. Monovalent P256 represents a safer form for in vivo applications

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