STREPTOKINASE-INDUCED, ANTIBODY-MEDIATED PLATELET AGGREGATION: A POTENTIAL CAUSE OF CLOT PROPAGATION IN VIVO

We identified a patient who exhibited paradoxical propagation of thrombus coincident with the administration of intracoronary streptokinase (SK) that was mediated by anti-SK antibodies. The patient had not been treated with SK in the past and had a plasma SK-neutralizing capacity of 160 U/ml. Using platelet-rich plasma (PRP) obtained from the patient, we found that SK initiated spontaneous platelet aggregation and secretion in vitro. Aggregation was specific for SK and not induced by urokinase or tissue plasminogen activator. In 14 of 15 controls, no platelet aggregation was observed in PRP with addition of SK. The addition of plasma or purified IgG from our index case to the PRP of all 14 controls supported SK-induced aggregation. This aggre-gatory response was not inhibited by aprotinin. Using purified proteins in a washed platelet system, we found that platelet aggregation was dependent on the presence of SK, specific anti-SK IgG, plasminogen, and platelets. These data demonstrate that anti-SK antibodies can promote platelet aggregation, presumably by binding to platelet-bound plasminogen-SK complexes. These data also imply that some individuals may possess anti-SK antibodies that are capable of inducing platelet aggregation in vivo and, thereby, promoting clot propagation or thromboembolic complications. In the absence of adequate, specific screening, this observation argues for the use of nonimmunogenic thrombolytic agents in the emergent setting.

Inhibition of Human Platelet Aggregation by the Proteolytic Effect of Streptokinase (SK). Role of the Factor VIII Related Antigen

10.1055/s-0039-1689380 ◽

1975 ◽

Cited By ~ 1

Author(s):

R. Castillo ◽

S. Maragall ◽

J. A. Guisasola ◽

F. Casals ◽

C. Ruiz ◽

...

Keyword(s):

Platelet Aggregation ◽

Factor Viii ◽

Platelet Rich Plasma ◽

Gel Filtration ◽

Inhibitory Effect ◽

Factor Viii Related Antigen ◽

Human Factor Viii ◽

Defective ADP-induced platelet aggregation has been observed in patients treated with streptokinase. This same effect appears “in vitro” when adding SK to platelet rich plasma (PRP). Classic hemophilia and normal platelet poor plasmas (PPP) treated with SK inhibit the aggregation of washed platelets; plasmin-treated normal human serum also shows an inhibitory effect on platelet aggregation. However, von Willebrand SK-treated plasmas do not inhibit the aggregation of washed platelets. The same results appear when plasmas are previously treated with a rabbit antibody to human factor VIII.This confirms that the antiaggregating effect is mainly linked to the digested factor VIII related antigen.The inhibition of ADP-induced platelet aggregation has been proved in gel filtration-isolated and washed platelets from SK-treated PRP.Defective ristocetin-induced platelet aggregation has also been observed- This action does not appear in washed platelets from SK-treated PRP in presence of normal PPP, but it does in presence of SK-treated PPP, which suggests that the inhibition of the ristocetin-induced aggregation is due to the lack of factor VIII and not to the factor VIII-related products.Heparin, either “in vivo” or “in vitro”, has corrected the antiaggregating effect of SK.

The pharmacology of L-670,596, a potent and selective thromboxane/prostaglandin endoperoxide receptor antagonist

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y89-155 ◽

1989 ◽

Vol 67 (9) ◽

pp. 989-993 ◽

Cited By ~ 30

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 ◽

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.

Lu 23051, A New Potent Inhibitor Of Platelet Aggregation

10.1055/s-0038-1653265 ◽

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 ◽

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

Effect of Diazepam on Platelet Function

10.1055/s-0039-1680490 ◽

1977 ◽

Author(s):

A. C. Carvalho ◽

R. W. Colman ◽

R. Vaillancourt ◽

R. Cabrai ◽

R. Anaya

Keyword(s):

Platelet Aggregation ◽

Platelet Function ◽

Platelet Rich Plasma ◽

Normal Subjects ◽

Serotonin Release ◽

Significant Inhibition ◽

Function Evaluation ◽

Diazepam (Valium) is one of the most prescribed medications in the world. Patients on Diazepam may need platelet function evaluation. Therefore, a study of its effect on both in vivo and in vitro platelet function was undertaken in 8 normal volunteers. Diazepam (10–40μg/ml) was incubated in vitro with platelet rich plasma (250,000/μl) at intervals of 15, 30, 60, 120, and 240 minutes followed by determination of platelet aggregation and 14C-serotonin release. Fifty percent inhibition of platelet aggregation and release by Diazepam was obtained at 1 hr with epinephrine (p<0.01) and at 2 hrs with ADP (p<0.01), but no significant effect was noted with collagen. The Diazepam inhibitory effect on platelet aggregation and release was overcome by high concentrations of aggregating agents, suggesting that its primary effect is not mediated by inhibition of prostaglandin synthesis.Following oral ingestion of 5mg of Diazepam, platelet aggregation and 14C-serotonin release were determined serially (2, 4, 8, 12, 24, and 48 hours) in the 8 normal subjects. After 8 hours, Diazepam inhibited ADP-induced aggregation and release by 39% (p<0.01) and epinephrine by 50% (p<0.01). No significant inhibition of collagen was observed. Forty-eight hours after Diazepam intake, platelet function returned to normal in all subjects.Our data show that Diazepam impairs both platelet aggregation and release in vitro and in vivo. Although the effect of Diazepam on in vivo hemostasis is still uncertain, our results suggest caution in the interpretation of platelet function testing in patients on this drug.

Enhancement of ADP-induced Platelet Aggregation by Adrenaline in Vivo and Its Prevention

10.1055/s-0038-1647788 ◽

1973 ◽

Vol 29 (02) ◽

pp. 490-498 ◽

Cited By ~ 6

Author(s):

Hiroh Yamazaki ◽

Itsuro Kobayashi ◽

Tadahiro Sano ◽

Takio Shimamoto

Keyword(s):

Platelet Count ◽

Platelet Aggregation ◽

Platelet Rich Plasma ◽

The Other ◽

Endothelial Surface ◽

Important Interaction ◽

Blood Coagulability ◽

The Difference

SummaryThe authors previously reported a transient decrease in adhesive platelet count and an enhancement of blood coagulability after administration of a small amount of adrenaline (0.1-1 µg per Kg, i. v.) in man and rabbit. In such circumstances, the sensitivity of platelets to aggregation induced by ADP was studied by an optical density method. Five minutes after i. v. injection of 1 µg per Kg of adrenaline in 10 rabbits, intensity of platelet aggregation increased to 115.1 ± 4.9% (mean ± S. E.) by 10∼5 molar, 121.8 ± 7.8% by 3 × 10-6 molar and 129.4 ± 12.8% of the value before the injection by 10”6 molar ADP. The difference was statistically significant (P<0.01-0.05). The above change was not observed in each group of rabbits injected with saline, 1 µg per Kg of 1-noradrenaline or 0.1 and 10 µg per Kg of adrenaline. Also, it was prevented by oral administration of 10 mg per Kg of phenoxybenzamine or propranolol or aspirin or pyridinolcarbamate 3 hours before the challenge. On the other hand, the enhancement of ADP-induced platelet aggregation was not observed in vitro, when 10-5 or 3 × 10-6 molar and 129.4 ± 12.8% of the value before 10∼6 molar ADP was added to citrated platelet rich plasma (CPRP) of rabbit after incubation at 37°C for 30 second with 0.01, 0.1, 1, 10 or 100 µg per ml of adrenaline or noradrenaline. These results suggest an important interaction between endothelial surface and platelets in connection with the enhancement of ADP-induced platelet aggregation by adrenaline in vivo.

The Effect of Barbituric Acid Derivatives on Platelet Function in Vitro and in Vivo

10.1055/s-0038-1649080 ◽

1973 ◽

Vol 30 (02) ◽

pp. 315-326

Author(s):

J. Heinz Joist ◽

Jean-Pierre Cazenave ◽

J. Fraser Mustard

Keyword(s):

Platelet Aggregation ◽

Platelet Function ◽

Barbituric Acid ◽

Platelet Rich Plasma ◽

Inhibitory Effect ◽

Primary Response ◽

Sodium Pentobarbital ◽

Barbituric Acid Derivatives

SummarySodium pentobarbital (SPB) and three other barbituric acid derivatives were found to inhibit platelet function in vitro. SPB had no effect on the primary response to ADP of platelets in platelet-rich plasma (PRP) or washed platelets but inhibited secondary aggregation induced by ADP in human PRP. The drug inhibited both phases of aggregation induced by epinephrine. SPB suppressed aggregation and the release reaction induced by collagen or low concentrations of thrombin, and platelet adherence to collagen-coated glass tubes. The inhibition by SPB of platelet aggregation was readily reversible and isotopically labeled SPB did not become firmly bound to platelets. No inhibitory effect on platelet aggregation induced by ADP, collagen, or thrombin could be detected in PRP obtained from rabbits after induction of SPB-anesthesia.

Dipyridamole Inhibits Platelet Aggregation in Whole Blood

10.1055/s-0038-1665327 ◽

1983 ◽

Vol 50 (04) ◽

pp. 852-856 ◽

Cited By ~ 104

Author(s):

P Gresele ◽

C Zoja ◽

H Deckmyn ◽

J Arnout ◽

J Vermylen ◽

...

Keyword(s):

Platelet Aggregation ◽

Whole Blood ◽

Ex Vivo ◽

Platelet Rich Plasma ◽

Significant Negative Correlation ◽

Significant Inhibition ◽

Oral Drug ◽

Human Blood Samples ◽

SummaryDipyridamole possesses antithrombotic properties in the animal and in man but it does not inhibit platelet aggregation in plasma. We evaluated the effect of dipyridamole ex vivo and in vitro on platelet aggregation induced by collagen and adenosine- 5’-diphosphate (ADP) in human whole blood with an impedance aggregometer. Two hundred mg dipyridamole induced a significant inhibition of both ADP- and collagen-induced aggregation in human blood samples taken 2 hr after oral drug intake. Administration of the drug for four days, 400 mg/day, further increased the antiplatelet effect. A significant negative correlation was found between collagen-induced platelet aggregation in whole blood and dipyridamole levels in plasma (p <0.001). A statistically significant inhibition of both collagen (p <0.0025) and ADP-induced (p <0.005) platelet aggregation was also obtained by incubating whole blood in vitro for 2 min at 37° C with dipyridamole (3.9 μM). No such effects were seen in platelet-rich plasma, even after enrichment with leukocytes. Low-dose adenosine enhanced in vitro inhibition in whole blood.Our results demonstrate that dipyridamole impedes platelet aggregation in whole blood by an interaction with red blood cells, probably involving adenosine.

Decreased Platelet Vitamin C in Diabetes Mellitus; Possible Role in Peraggregatoon

10.1055/s-0039-1687640 ◽

1979 ◽

Author(s):

K.E. Sarji ◽

J. Gonzalez ◽

H. Hempling ◽

J.A. Colwell

Keyword(s):

Ascorbic Acid ◽

Arachidonic Acid ◽

Platelet Aggregation ◽

Vitamin C ◽

Platelet Rich Plasma ◽

Solution Ph ◽

Dose Dependent Fashion ◽

Insulin Dependent Diabetic ◽

To determine whether Vitamin C might relate to the increased platelet sensitivity in the diabetic, we have measured levels of platelet Vitamin C and studied the effects of Vitamin C on platelet aggregation. Ascorbic acid levels in washed platelets from diabetics were significantly lower than from normals (4s.2±3 μg/1010 platelets vs. 2s.s±2 μg/1010 platelets, p<.001). The effects of ascorbic acid on platelet aggregation in vitro were studied by adding ascorbic acid in buffered solution (pH 7.35) prior to-aggregating agents. Ascorbic acid in platelet-rich plasma consistently inhibited platelet aggregation with threshold concentrations of ADP, epinephrine, and collagen. With washed platelets, ascorbic acid inhibited arachidonic, acid-induced aggregation. When platelets were incubated at 37°C for 10 minutes with varying concentrations of ascorbic acid, rewashed, and aggregation with arachidonic acid tested, aggregation was inhibited in a linear dose-dependent fashion. Oral ingestion of ascorbic acid (2 gm/day) for seven days by normal non-smoking males produced a marked inhibition of aggregation. In a similar study, platelets from an insulin-dependent diabetic showed no change in aggregation. These results suggest that platelet levels of ascorbic acid may relate to the hyperaggregat ion of platelets from diabetics.

Effects of Ethanol on Pathways of Platelet Aggregation In Vitro

10.1055/s-0038-1647500 ◽

1988 ◽

Vol 59 (03) ◽

pp. 383-387 ◽

Cited By ~ 42

Author(s):

Margaret L Rand ◽

Marian A Packham ◽

Raelene L Kinlough-Rathbone ◽

J Fraser Mustard

Keyword(s):

Arachidonic Acid ◽

Platelet Aggregation ◽

Platelet Rich Plasma ◽

Secondary Phase ◽

Primary Phase ◽

Rabbit Platelet ◽

Membrane Phospholipids ◽

Rabbit Platelets ◽

SummaryEthanol, at physiologically tolerable concentrations, did not affect the primary phase of ADP-induced aggregation of human or rabbit platelets, which is not associated with the secretion of granule contents. Potentiation by epinephrine of the primary phase of ADP-induced aggregation of rabbit platelets was also not inhibited by ethanol. However, ethanol did inhibit the secondary phase of ADP-induced aggregation which occurs with human platelets in citrated platelet-rich plasma and is dependent on the formation of thromboxane A2. Inhibition by ethanol of thromboxane production by stimulated platelets is likely due to inhibition of the mobilization of arachidonic acid from membrane phospholipids, as ethanol had little or no effect on aggregation and secretion induced by arachidonic acid or the thromboxane mimetic U46619. Rabbit platelet aggregation and secretion in response to low concentrations of collagen, thrombin, or PAF were inhibited by ethanol. Inhibition of the effects of thrombin and PAF was also observed with aspirin-treated platelets. Thus, in addition to inhibiting the mobilization of arachidonate for thromboxane formation that occurs with most agonists, ethanol can also inhibit aggregation and secretion through other effects on platelet responses.

Studies investigating platelet aggregation and release initiated by sera from patients with thrombotic thrombocytopenic purpura

Blood ◽

10.1182/blood.v69.3.924.bloodjournal693924 ◽

1987 ◽

Vol 69 (3) ◽

pp. 924-928 ◽

Cited By ~ 1

Author(s):

JG Kelton ◽

JC Moore ◽

WG Murphy

Keyword(s):

Platelet Aggregation ◽

Thrombotic Thrombocytopenic Purpura ◽

Disease Process ◽

The Other ◽

Platelet Glycoprotein ◽

Glycoprotein Ib ◽

Thrombocytopenic Purpura ◽

Many patients with thrombotic thrombocytopenic purpura (TTP) have a platelet aggregating factor in their serum that may be pathologically linked with the disease process. To help characterize the type of platelet aggregation and platelet release induced by the sera from seven TTP patients, we measured the ability of a variety of inhibitors of platelet function as well as the ability of monoclonal antibodies (MoAbs) against platelet glycoproteins to inhibit TTP sera-induced platelet aggregation and release. These results were compared with the ability of the same inhibitors to block platelet aggregation induced by ristocetin, collagen, ADP, thrombin, and IgG-immune complexes. Monoclonal antibody directed against platelet glycoprotein Ib totally inhibited ristocetin-induced aggregation and release but had no effect on aggregation and release induced by the TTP sera or by any of the other platelet agonists. However, the MoAb against glycoproteins IIb/IIIa inhibited aggregation and release caused by TTP sera as well as by collagen, thrombin, and ADP but had no effect on aggregation and release induced by ristocetin. The aggregating activity could be abolished by heparin but not by the serine protease inhibitor PMSF (1 mmol/L). And although monomeric human IgG and purified Fc fragments of IgG inhibited IgG-immune complex-induced aggregation and release, they had no effect on TTP sera-induced aggregation and release nor on aggregation and release induced by any of the other agonists. Consistent with these in vitro studies showing no effect of IgG were the in vivo observations that intravenous (IV) IgG was without effect when administered to three patients with TTP. This study indicates that although a von Willebrand factor (vWF)-rich preparation of cryoprecipitate enhances the in vitro platelet aggregation and release caused by sera from the seven TTP patients we studied, the pathway of aggregation and release is not via platelet glycoprotein Ib. Also the aggregating factor of TTP sera is not neutralized in vitro or in vivo by IgG.