Further Evidence for the Role of Thrombin in the Platelet Release Reaction Caused by Various Agents, and the Nature of Biphasic Platelet Aggregation

1978 ◽  
Vol 38 (3) ◽  
pp. 381-390 ◽  
Author(s):  
Huzoor-Akbar ◽  
Neville G. Ardlie
Keyword(s):  
Platelet Aggregation ◽  
Release Reaction ◽  
Platelet Release

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.

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.

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.

The Effects of Glycoprotein IIb/IIIa Antagonist RGDS on Platelet Aggregation and Release Reaction In Vitro.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3908-3908
Author(s):  
Shuangfeng Xie ◽  
Songmei Yin ◽  
Danian Nie ◽  
Yiqing Li ◽  
Xiuju Wang ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Adhesion ◽  
Adenosine Diphosphate ◽  
Platelet Glycoprotein ◽  
High Concentration ◽  
Release Reaction ◽  
Dense Granules ◽  
Negative Effect ◽  
Platelet Release

Abstract Platelet activation, including platelet adhesion, platelet aggregation and platelet release reaction, played an important role in thrombogenesis. We all knew that Platelet glycoprotein IIb/IIIa antagonist was the most effective drug for anti-aggregation, while we don’t know clearly its effect on platelet release reaction and the relations between its effects on platelet aggregation and release reaction. Platelet release reactions included α-granules and dense granules releasing. When α-granules were released, its membrane glycoprotein CD62p was expressed in the platelet membrane. We used the CD62p expression as the index of platelet release reaction. In the current study, the 4-peptides RGDS (Arg-Gly-Asp-Ser) was used as glycoprotein IIb/IIIa antagonist. We detected the effects of RGDS on platelet aggregation and CD62p expression induced by adenosine diphosphate (ADP) (finial concentration, 5μmol/L) in vitro. 50, 100, 200, 400 and 800μmol/L RGDS were used separately in the test. RGDS of each concentration could significantly inhibited maximal platelet aggregation (PAG(M)) induced by ADP, the 50% inhibiting concentration was approximately 200μmol/L. 800μmol/L RGDS could inhibited PAG(M) by 80.48±8.18%. Only ≥200μmol/L RGDS could significantly inhibited platelet CD62p expression. 800μmol/L RGDS could inhibit platelet CD62p expression by 27.31±9.74%. The inhibiting effect of RGDS on PAG(M) and platelet CD62p expression had significantly correlation (r =0.976, P<0.05). These results indicated that RGDS in low concentration (<200μmol) had little negative effect on platelet release reaction induced by ATP, while in relatively high concentration (≥200μmol) RGDS could inhibit platelet release reaction. When RGDS concentrations were same its effect on platelet release reaction was much less than that on platelet aggregation, which indicated that platelet glycoprotein IIb/IIIa compound could only partly participated in the platelet release reaction but fully participated in platelet aggregation induced by ADP.

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