Platelet Reactions and Immune Processes

1970 ◽  
Vol 23 (01) ◽  
pp. 110-119 ◽  
Author(s):  
F Jobin ◽  
France Tremblay ◽  
M Morissette
Keyword(s):  
Platelet Aggregation ◽  
Platelet Aggregation Inhibitors ◽  
Human Platelets ◽  
Present Knowledge ◽  
Release Reaction ◽  
Cellular Processes ◽  
Cell Release ◽  
Aggregation Inhibitors ◽  
Platelet Release

SummaryWe have studied the effect of chymotrypsin substrates and inhibitors on the aggregation of human platelets by collagen, latex, and epinephrine :1. We have found that platelet aggregation was inhibited by most chymotrypsin substrates and inhibitors which we studied.2. In general, there was a positive correlation between the effectiveness of the compounds as chymotrypsin substrates or inhibitors on one hand, and as platelet aggregation inhibitors on the other hand. However aromatic amino acid derivatives acetylated on the α-amine group were much less effective with platelets than they are with chymotrypsin.3. Chymotrypsin substrates and inhibitors also inhibit the anaphylactic release of histamine. The view is presented that the platelet release reaction and the mast cell release reaction have several common biological and biochemical features.4. The possible role of platelet esterases in platelet thrombogenetic reactions is discussed in the light of the present knowledge of the role of cell bound esterase in several inflammatory or immune cellular processes.

Release, Aggregation and Lysis of Human Platelets by Antilymphocyte Globulin and Antiplatelet Serum

1976 ◽  
Vol 36 (02) ◽  
pp. 411-423 ◽  
Author(s):  
Nicholas Lekas ◽  
J. C Rosenberg
Keyword(s):  
Platelet Aggregation ◽  
Gamma Globulin ◽  
Human Platelets ◽  
Plasma Medium ◽  
Release Reaction ◽  
Clinical Events ◽  
Thrombotic Complications ◽  
Platelet Release ◽  
Free Media

SummaryHuman platelets labeled with 51Cr were used to determine the contribution made by platelet lysis to the platelet release reaction and platelet aggregation induced by rabbit antihuman platelet serum (APS) and equine antihuman thymocyte globulin (ATG). Platelets were tested in both plasma (PRP) and non-plasma containing media. Antibodies directed against platelets, either as APS or ATG, induced significant amounts of platelet release and aggregation, as well as some degree of lysis, in the absence of complement. The presence of complement increased platelet lysis and aggregation, but not the release reaction. Non-immune horse gamma globulin produced different responses depending upon whether platelets were investigated in PRP or non-plasma containing media. Aggregation was seen in the latter but not the former. These differences can be explained by the presence of plasma components which prevent non-specific immune complexes from causing platelet aggregation. Since platelets in vivo are always in a plasma medium, one must be wary of utilizing data from platelet studies in synthetic plasma-free media as the basis of explaining clinical events. These observations demonstrate at least two, and possibly three, different mechanisms whereby ATG could activate platelets causing thrombotic complications and thrombocytopenia, i.e., via 1) specific and, 2) non-specific non-lytic pathways and 3) a lytic pathway.

The Role Of Glycoprotein V (GPV) In Thrombin Activation Of Human Platelets

1981 ◽  
Author(s):  
K Fujimura ◽  
S Maehama ◽  
A Kuramoto
Keyword(s):  
Membrane Surface ◽  
Human Platelets ◽  
Surface Proteins ◽  
Galactose Oxidase ◽  
Membrane Glycoproteins ◽  
Release Reaction ◽  
Sds Page ◽  
Thrombin Activation ◽  
Platelet Release

The analysis of platelet membrane glycoproteins and platelet functions was conducted to disclose the role of GPI and V in the thrombin activation of platelet. Our previous study proved that native and HNB thrombin hydrolyzed GPV(M. W.8-9 × 104) selectively and released new glycoprotein fragment (M.W. 6.2-6.8 × 104 ) of GPV, resulting in the development of 14C-5HT release reaction and platelet MDA production. But DIP thrombin could not induce these phenomena.Membrane surface proteins of intact platelets were labeled with Na[3H]BH4 by neuraminidase and galactose oxidase method and analyzed by fluorography after SDS-PAGE.The high molecular weight glycoproteins, GPI, GPIII and GPV were diminished by trypsin treatment in correlation with the concentration and incubation time. In correspond to the diminution of these membrane glycoproteins, platelet release reaction was increased .Chymotrypsin treatment in various concentrations, release reaction and MDA production were not induced in spite of long incubation times. But the ristocetin aggregation was decreased in Chymotrypsin treated platelets whose membrane glycoproteins did not change significantly. The Chymotrypsin treated platelets whose GPI was modified functionally, showed normal release reaction and MDA production by thrombin stimulation. On the other hand, the thrombin treated platelets in low concentration previously whose GPV was hydrolyzed partially, demonstrated little release reaction and MDA production by thrombin or trypsin stimulation. From these results, the GPV was hydrolyzed specifically by thrombin and nonspecifically by trypsin but was not hydrolyzed by Chymotrypsin. It was concluded that the thrombin binds to the GPI and hydrolyzed GPV specifically, and hydrolysis of GPV might act as a signal to induce the platelet release reaction and prostaglandin metabolism.

scholarly journals Platelet release reaction and intracellular cGMP

Blood ◽  
1978 ◽  
Vol 52 (3) ◽  
pp. 524-531 ◽  
Author(s):  
A Weiss ◽  
NL Baenziger ◽  
JP Atkinson
Keyword(s):  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Serotonin Release ◽  
Secretory Process ◽  
Release Reaction ◽  
Intracellular Cgmp ◽  
Exogenous Addition ◽  
Human Thrombin ◽  
Platelet Release

Abstract Enchanced cAMP concentrations inhibit the aggregation and release reaction of isolated human platelets and platelet-rich plasma to all known inducing agents. An opposing role for cGMP in this phenomenon has been proposed by some but not by others, and the function of cGMP in this secretory process is unclear. To further elucidate the role of cGMP in the release reaction, the effect of increased concentrations of this cyclic nucleotide on 14C-serotonin release was evaluated utilizing isolated human platelets and highly purified human thrombin or commercially available bovine thrombin. Several recently described stimulators of guanylate cyclase, including sodium nitroprusside, sodium azide, nitrosoquanidines, and ascorbic acid, were found to markedly augment platelet cGMP levels. Enhanced platelet cGMP concentrations produced by these drugs or by the exogenous addition of cGMP and its analogues neither caused these cells to secrete nor modulated the thrombin-induced serotonin release reaction. The inhibition of serotonin release by increased cAMP concentrations was not counteracted by increased cGMP levels. Platelet cGMP concentrations were unaltered by thrombin. These data indicate that cGMP is not an obligatory signal or a modulator of the thrombin-induced platelet release reaction.

Fibrin-induced release of platelet serotonin

1976 ◽  
Vol 231 (2) ◽  
pp. 344-350 ◽  
Author(s):  
KG Orloff ◽  
D Michaeli
Keyword(s):  
Platelet Aggregation ◽  
Prostaglandin E1 ◽  
Human Platelets ◽  
The Self ◽  
Human Fibrinogen ◽  
Release Reaction ◽  
Activated Platelets ◽  
Platelet Serotonin ◽  
Platelet Release ◽  
Adhesion Of Platelets

Human platelets were reacted with polymerized fibrin formed from human fibrinogen. The platelets adhered to the fibrin particles and this adhesion was followed by the release of serotonin from prelabeled platelets. The adhesion of platelets to fibrin was not inhibited by adenosine or prostaglandin E1. However, the subsequent Ca2+-dependent release of platelet serotonin was completely inhibited by these compounds. After the initial platelet-fibrin interaction, ADP and serotonin released from activated platelets may lead to additional platelet aggregation and release. Therefore, in addition to clot stabilization, fibrin serves as an initiator of the platelet release reaction. This in turn initiates the self-amplifying process of platelet aggregation.

scholarly journals Influence of Platelet Aggregation Modulators on Cyclic AMP Production in Human Thrombocytes

Folia Medica ◽  
2018 ◽  
Vol 60 (2) ◽  
pp. 241-247
Author(s):  
Krasimir O. Boyanov ◽  
Ana I. Maneva
Keyword(s):  
Platelet Aggregation ◽  
Cyclic Amp ◽  
Ion Transport ◽  
Redox State ◽  
Platelet Aggregation Inhibitors ◽  
Human Platelets ◽  
Signal Pathways ◽  
Phosphatidylinositol 3 Kinase ◽  
Elisa Kit ◽  
Aggregation Inhibitors

Abstract Background: Cyclic AMP is a powerful inhibitor of platelet aggregation. In the present study we examined the effect of platelet aggregation modulators on cyclic AMP content in human thrombocytes. Of the agents we tested, lactoferrin, wortmannin, quercetin and amiloride are platelet aggregation inhibitors, whereas ouabain is a platelet activator. Aim: To investigate the effect of lactoferrin, wortmannin, quercetin, ouabain and amiloride applied alone and in combination with lactoferrin on cyclic AMP production in human platelets. Materials and methods: ‘Direct cAMP ELISA kit’ was used for cyclic AMP determination. Results: The studied modulators, individually or in combination, stimulate cyclic AMP production in platelets. Conclusions: Wortmannin, quercetin, ouabain and amiloride increase cyclic AMP level in human platelets. Lactoferrin also increases cyclic AMP level, but the effect is statistically insignificant, which shows that lactoferrin does not participate directly in the cyclic AMP signaling. Lactoferrin additionally augments the stimulating action of wortmannin, quercetin, ouabain and amiloride on the cyclic AMP production. This probably shows a synergetic interference of lactoferrin in signal pathways along with phosphatidylinositol 3-kinase (wortmannin), quercetin (control over protein kinases, the redox state of the cell and ion transport), ouabain and amiloride (mechanisms of ion transport and phosphorylation).

Requirements for Aggregation of Washed Human Platelets Suspended in Buffered Salt Solutions

1972 ◽  
Vol 28 (01) ◽  
pp. 002-013 ◽  
Author(s):  
Christina B Harbury ◽  
J. Edward Hershgold ◽  
Stanley L Schrier
Keyword(s):  
Plasma Membrane ◽  
Platelet Aggregation ◽  
Salt Solution ◽  
Human Platelets ◽  
Salt Solutions ◽  
Release Reaction ◽  
No Release ◽  
New Finding ◽  
Threshold Doses ◽  
Platelet Release

SummaryWith the use of washed human platelets suspended in a buffered salt solution, we have studied the factors capable of acting directly at the platelet plasma membrane to produce aggregation as opposed to those which produce the platelet release reaction and secondary aggregation. Platelet aggregation was measured in an aggregometer and the release reaction followed by assays of the release products.Ca and fibrinogen will not independently induce aggregation in washed human platelets suspended in a buffered salt solution. However, in their absence ADP-, 5HT-and epinephrine-mediated aggregation will not proceed. Of particular interest was the finding that in the presence of Ca, threshold doses of thrombin will produce aggregation earlier if μg amounts of fibrinogen are added. Ca and fibrinogen therefore appear to be absolutely required for aggregation, whether the aggregation is produced by the addition or by the release of required components.If either ADP, 5HT or epinephrine is added singly to buffer-suspended platelets in the presence of Ca and fibrinogen, 10–20% aggregation is observed. The combination of either ADP-5HT, ADP-epinephrine or 5HT-epinephrine produces 60–70% aggregation. The addition of ADP, 5HT and epinephrine together produces 80–90% aggregation.No release reaction is produced by the addition of ADP or 5HT alone or in combination. A new finding in this study therefore is that 5HT and ADP can act directly at the platelet plasma membrane to produce extensive aggregation in the absence of any release reaction.Epinephrine does produce a small release reaction, and may therefore produce its enhancement of aggregation either by acting directly at the platelet plasma membrane or by the release of something other than Ca, fibrinogen, ADP, 5HT, or epinephrine.In this study using washed human platelets suspended in a buffered salt solution, no evidence was found for the requirement of a plasma protein other than fibrinogen in platelet aggregation.

scholarly journals Platelet release reaction and intracellular cGMP

Blood ◽  
1978 ◽  
Vol 52 (3) ◽  
pp. 524-531
Author(s):  
A Weiss ◽  
NL Baenziger ◽  
JP Atkinson
Keyword(s):  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Serotonin Release ◽  
Secretory Process ◽  
Release Reaction ◽  
Intracellular Cgmp ◽  
Exogenous Addition ◽  
Human Thrombin ◽  
Platelet Release

Enchanced cAMP concentrations inhibit the aggregation and release reaction of isolated human platelets and platelet-rich plasma to all known inducing agents. An opposing role for cGMP in this phenomenon has been proposed by some but not by others, and the function of cGMP in this secretory process is unclear. To further elucidate the role of cGMP in the release reaction, the effect of increased concentrations of this cyclic nucleotide on 14C-serotonin release was evaluated utilizing isolated human platelets and highly purified human thrombin or commercially available bovine thrombin. Several recently described stimulators of guanylate cyclase, including sodium nitroprusside, sodium azide, nitrosoquanidines, and ascorbic acid, were found to markedly augment platelet cGMP levels. Enhanced platelet cGMP concentrations produced by these drugs or by the exogenous addition of cGMP and its analogues neither caused these cells to secrete nor modulated the thrombin-induced serotonin release reaction. The inhibition of serotonin release by increased cAMP concentrations was not counteracted by increased cGMP levels. Platelet cGMP concentrations were unaltered by thrombin. These data indicate that cGMP is not an obligatory signal or a modulator of the thrombin-induced platelet release reaction.

The Effect of the Phospholipase Inhibitor Mepacrine on Platelet Aggregation, the Platelet Release Reaction and Fibrinogen Binding to the Platelet Surface

1981 ◽  
Vol 45 (03) ◽  
pp. 257-262 ◽  
Author(s):  
P D Winocour ◽  
R L Kinlough-Rathbone ◽  
J F Mustard
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Surface ◽  
Release Reaction ◽  
Fibrinogen Binding ◽  
Platelet Release

SummaryWe have examined whether inhibition by mepacrine of freeing of arachidonic acid from platelet phospholipids inhibits platelet aggregation to collagen, thrombin or ADP, and the release reaction induced by thrombin or collagen. Loss of arachidonic acid was monitored by measuring the amount of 14 C freed from platelets prelabelled with 14 C-arachidonic acid. Mepacrine inhibited 14 C loss by more than 80% but did not inhibit thrombin-induced platelet aggregation and had a small effect on release. ADP-induced platelet aggregation did not cause 14 C loss. Mepacrine inhibited ADP-induced platelet aggregation by inhibiting the association of fibrinogen with platelets during aggregation. The effect of mepacrine on fibrinogen binding could be considerably decreased by washing the platelets but the inhibition of 14 C loss persisted. Platelets pretreated with mepacrine and then washed show restoration of aggregation to collagen. Thus, mepacrine has two effects; 1. it inhibits phospholipases, 2. it inhibits fibrinogen binding. Freeing of arachidonic acid is not necessary for platelet aggregation or the release reaction.

New Platelet Aggregation Inhibitors

1997 ◽  
Vol 17 (01) ◽  
pp. 43-48 ◽  
Author(s):  
R. Verhaeghe ◽  
J. Vermylen
Keyword(s):  
Platelet Aggregation ◽  
Platelet Aggregation Inhibitors ◽  
Aggregation Inhibitors
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