Human Platelet Acetylcholinesterase: The Effects of Anticholinesterases on Platelet Function

1979 ◽  
Vol 42 (05) ◽  
pp. 1615-1619 ◽  
Author(s):  
Martin J Smith ◽  
Boyd Braem ◽  
Kent D Davis
Keyword(s):  
Platelet Function ◽  
Ache Activity ◽  
Room Temperature ◽  
Platelet Rich Plasma ◽  
Complete Inhibition ◽  
Clot Retraction ◽  
Plasma Clot ◽  
Normal Platelet ◽  
Aggregation Factor

SummaryPlatelet acetylcholinesterase (AChE) activity was measured in gel-filtered platelet preparations. Three different anticholinesteratic agents (eserine, neostigmine, and diiso- propylphosphorofluoridate) at final concentrations of 10 μM caused complete inhibition of AChE activity after 30 min incubation at room temperature with either platelet-rich plasma or gel-filtered platelets. Complete inhibition of platelet AChE had no effect on platelet aggregation, factor-3 availability, and plasma clot retraction. We conclude that platelet membrane AChE activity is not required for normal platelet function as measured by these in vitro parameters.

Effect of Lidoflazine (R 7904) on Human Platelet Function in Vitro

1972 ◽  
Vol 28 (02) ◽  
pp. 228-236 ◽  
Author(s):  
F De Clerck
Keyword(s):  
Platelet Function ◽  
Mode Of Action ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Serotonin Release ◽  
Clot Retraction ◽  
Plasma Coagulation ◽  
Release Reaction ◽  
Platelet Release

SummaryThe effect of lidoflazine and of cinnarizine on human platelet function in vitro was compared to that of dipyridamole.Pre-incubation for 30 min at 37° C of platelet rich plasma with lidoflazine or with dipyridamole 5 ×10–4 M resulted in an appreciable inhibition of collagen aggregation in particular and to a lesser extent of ADP aggregation; cinnarizine was marginally active only.Clot retraction was inhibited by lidoflazine and by dipyridamole. Experiments on biphasic ADP aggregation and C14-serotonin release during aggregation show that lidoflazine reduces the platelet release reaction.The possible mode of action of the compound is discussed.Plasma coagulation and PF – 3 availability were not affected.

Binding of Anti-Actin Auto-Antibodies to Platelets

1975 ◽  
Author(s):  
C. A. Bouvier ◽  
G. Gabbiani ◽  
G. Majno
Keyword(s):  
Striated Muscle ◽  
Platelet Rich Plasma ◽  
Major Change ◽  
Fluorescent Staining ◽  
Clot Retraction ◽  
Plasma Clot ◽  
Induce Platelet Aggregation ◽  
Smooth Muscle Antibody ◽  
Induced Aggregation

It was recently shown (Gabbiani & Coll., Am. J. Path. 72, 473-488, 1973) that a natural antibody occurring in patients with chronic hepatitis is specifically directed against smooth and striated muscle actin or, in the case of platelets, Thrombosthenin A. Thus it is proposed to change its name from Smooth Muscle Antibody (SMA) to Anti Actin Antibody (AAA). The possibility that AAA would contain a contaminant directed against cell membranes was ruled out because it does not bind (nor its titer in supernatant decrease) to intact platelets, but only to damaged ones (by freeze-thawing). However AAA binds to a platelet-rich clot, and bright fluorescent staining is obtained both for such clots and bone-marrow megacaryocytes. AAA does not induce platelet aggregation in vitro when added to platelet-rich plasma; it does not inhibit or potentiate ADP, Adrenalin or Collagen induced aggregation, and does not inhibit platelet-rich plasma clot retraction.With aggregation controlled in an aggregometer, the following observations were made : AAA adsorption (and consequent fluorescent staining) begins immediately after addition of the trigger, and becomes maximal when a plateau is reached (so-called irreversible aggregation). However, when liminary amounts of ADP are added, so as to obtain reversible aggregation, a large number of disaggregated platelets do bind with AAA, suggesting that actin-related antigens have become available to antibody. This implies that a major change in membrane permeability to large molecules has occurred. The same holds true when ADP-induced aggregation is prevented by EDTA.

The tetraspanin superfamily member CD151 regulates outside-in integrin αIIbβ3 signaling and platelet function

Blood ◽  
2004 ◽  
Vol 104 (8) ◽  
pp. 2368-2375 ◽  
Author(s):  
Lai-Man Lau ◽  
Janet L. Wee ◽  
Mark D. Wright ◽  
Gregory W. Moseley ◽  
P. Mark Hogarth ◽  
...  
Keyword(s):  
Platelet Function ◽  
Fluorescein Isothiocyanate ◽  
Dense Granule ◽  
Free Calcium ◽  
Clot Retraction ◽  
Altered Expression ◽  
Integrin Αiibβ3 ◽  
Normal Platelet ◽  
Granule Secretion

Abstract The tetraspanin family member CD151 forms complexes with integrins and regulates cell adhesion and migration. While CD151 is highly expressed in megakaryocytes and to a lesser extent in platelets, its physiologic role in platelets is unclear. In this study, we investigate the physical and functional importance of CD151 in murine platelets. Immunoprecipitation/Western blot studies reveal a constitutive physical association of CD151 with integrin αIIbβ3 complex under strong detergent conditions. Using CD151-deficient mice, we show that the platelets have impaired “outside-in” integrin αIIbβ3 signaling with defective platelet aggregation responses to protease-activated receptor 4 (PAR-4) agonist peptide, collagen, and adenosine diphosphate (ADP); impaired platelet spreading on fibrinogen; and delayed kinetics of clot retraction in vitro. This functional integrin αIIbβ3 defect could not be attributed to altered expression of integrin αIIbβ3. CD151–/– platelets displayed normal platelet alpha granule secretion, dense granule secretion, and static platelet adhesion. In addition, CD151–/– platelets displayed normal “inside-out” integrin αIIbβ3 signaling properties as demonstrated by normal agonist-induced binding of soluble fluorescein isothiocyanate (FITC)–fibrinogen, JON/A antibody binding, and increases in cytosolic-free calcium and inositol 1,4,5 triphosphate (IP3) levels. This study provides the first direct evidence that CD151 is essential for normal platelet function and that disruption of CD151 induced a moderate outside-in integrin αIIbβ3 signaling defect.

In Vitro Effects of Dihomo-γLinolenic Acid (DHLA) on Normal and Diabetic Platelet Function

1979 ◽  
Author(s):  
M. Zuzel ◽  
P.B.A. Kernoff ◽  
A.L. Willis ◽  
R.C. Paton ◽  
G.P. McNicol
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Platelet Rich Plasma ◽  
In Vitro Tests ◽  
Diabetic Patients ◽  
Normal Platelet ◽  
In Vitro Effects ◽  
Kinetics Of ◽  
Primary Platelet

DHLA causes a general inhibition of platelet reactions in standard in vitro tests of platelet function. Significantly more DHLA is required for the 50% inhibition (ID 50) of diabetic when compared to normal platelet reactions (Kernoff et al. Thrombosis & Haemostasis 38, 194, 1977). To investigate the cause of this difference we have studied kinetics of ADP-induced primary platelet aggregation, its inhibition by DHLA, and the formation of malondialdehyde (MDA) in the presence of DHLA in platelet-rich plasma of six healthy subjects and six diabetic patients with advanced microangiopathy. The results showed a significantly lower Km (ADP) for platelet aggregation in the diabetic group compared to normal. The (DHLA) of the competitive component of inhibition of platelet aggregation (prostaglandin production-mediated) was not significantly different In the two groups. Also, amounts of MDA formed in diabetic and normal PRP in the presence of DHLA were not significantly different. We conclude that the apparent low susceptibility of diabetic platelets to inhibition by DHLA might be a result of a primary hyper-reactivity of these platelets due to a cause other than an abnormality of the platelet PG production pathway.

Effect of Aspirin on the Thrombelastogram of Human Blood

1973 ◽  
Vol 30 (03) ◽  
pp. 494-498 ◽  
Author(s):  
G de Gaetano ◽  
J Vermylen
Keyword(s):  
Oral Dose ◽  
Single Oral Dose ◽  
Platelet Function ◽  
Human Blood ◽  
Platelet Rich Plasma ◽  
Plasma Samples ◽  
Release Reaction ◽  
Platelet Release

SummaryThrombelastograms of both native blood and re-calcified platelet-rich plasma samples taken from subjects given a single oral dose of aspirin (1 gram) were not significantly different from the pretreatment recordings. Aspirin also did not modify the thrombelastogram when preincubated in vitro with platelet-rich plasma at concentrations inhibiting the platelet “release reaction” by collagen. Thrombelastography therefore cannot evaluate the effect of aspirin on platelet function.

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

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.

Interactions of Staphylokinase with Human Platelets

1995 ◽  
Vol 73 (03) ◽  
pp. 472-477 ◽  
Author(s):  
H R Lijnen ◽  
B Van Hoef ◽  
D Collen
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Specific Binding ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Normal Plasma ◽  
Atp Secretion ◽  
Platelet Disaggregation ◽  
Activation Rate

SummaryThe interactions of recombinant staphylokinase (SakSTAR) with human platelets were investigated in a buffer milieu, in a human plasma milieu in vitro, and in plasma from patients with acute myocardial infarction (AMI) treated with SakSTAR.In a buffer milieu, the activation rate of plasminogen by SakSTAR or streptokinase (SK) was not significantly altered by addition of platelets. Specific binding of SakSTAR or SK to either resting or thrombin- activated platelets was very low. ADP-induced or collagen-induced platelet aggregation in platelet-rich plasma (PRP) was 94 ± 2.7% or 101 ± 1.7% of control in the presence of 0.1 to 20 μM SakSTAR, with corresponding values of 95 ± 2.8% or 90 ± 4.6% of control in the presence of 0.1 to 4 μM SK. No effects were observed on platelet disaggregation. ATP secretion following collagen-induced platelet aggregation was 4.3 ± 0.26 μM for SakSTAR (at concentrations of 0.1 to 20 μM) and 4.4 ± 0.35 μM for SK (at concentrations of 0.1 to 4 μM), as compared to 3.4 ± 0.70 μM in the absence of plasminogen activator.Fifty % lysis in 2 h (C50) of 60 μl 125I-fibrin labeled platelet-poor plasma (PPP) clots prepared from normal plasma or from plasma of patients with Glanzmann thrombasthenia and immersed in 0.5 ml normal plasma, was obtained with 12 or 16 nM SakSTAR and with 49 or 40 nM SK, respectively. C50 values for lysis of 60 μl PRP clots prepared from normal or patient plasma were also comparable for SakSTAR (19 or 21 nM), whereas SK was 2-fold more potent toward PRP clots prepared from Glanzmann plasma as compared to normal plasma (C50 of 130 versus 270 nM).No significant effect of SakSTAR on platelet function was observed in plasma from patients with AMI treated with SakSTAR, as revealed by unaltered platelet count, platelet aggregation and ATP secretion.Thus, no effects of high SakSTAR concentrations were observed on human platelets in vitro, nor of therapeutic SakSTAR concentrations on platelet function in plasma.

Abstract 13598: The G-protein BetaGamma Subunits Regulate Platelet Function

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Ahmed Alarabi ◽  
Zubair Karim ◽  
Victoria Hinojos ◽  
Patricia A Lozano ◽  
Keziah Hernandez ◽  
...  
Keyword(s):  
G Protein ◽  
Platelet Function ◽  
Thrombus Formation ◽  
Human Platelets ◽  
Inhibitory Effects ◽  
Clot Retraction ◽  
Betagamma Subunits

Platelet activation involves tightly regulated processes to ensure a proper hemostasis response, but when unbalanced, can lead to pathological consequences such as thrombus formation. G-protein coupled receptors (GPCRs) regulate platelet function by interacting with and mediating the response to various physiological agonists. To this end, an essential mediator of GPCR signaling is the G protein Gαβγ heterotrimers, in which the βγ subunits are central players in downstream signaling pathways. While much is known regarding the role of the Gα subunit in platelet function, that of the βγ remains poorly understood. Therefore, we investigated the role of Gβγ subunits in platelet function using a Gβγ (small molecule) inhibitor, namely gallein. We observed that gallein inhibits platelet aggregation and secretion in response to agonist stimulation, in both mouse and human platelets. Furthermore, gallein also exerted inhibitory effects on integrin αIIbβ3 activation and clot retraction. Finally, gallein’s inhibitory effects manifested in vivo , as documented by its ability to modulate physiological hemostasis and delay thrombus formation. Taken together, our findings demonstrate, for the first time, that Gβγ directly regulates GPCR-dependent platelet function, in vitro and in vivo . Moreover, these data highlight Gβγ as a novel therapeutic target for managing thrombotic disorders.

scholarly journals Are Platelet Aggregation Tests the Best Way to Assess New Drugs for Arterial Disease

2018 ◽  
Vol 1 (1) ◽  
pp. 01-03
Author(s):  
Mark I. M. Noble
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Platelet Rich Plasma ◽  
New Drugs ◽  
In Vitro Test ◽  
In Vivo Efficacy ◽  
Experimental Animals ◽  
Stenosed Artery

Over many years, laboratory testing of platelet aggregability have been carried out in attempts to develop drugs that would prevent thrombosis in arteries. The problems encountered included the question of methodology. Blood samples have to be anticoagulated in order to study the platelets. Anti-coagulation with citrate and tests on derived platelet rich plasma did not correlate at all well with thrombus growth in the stenosed coronary arteries of experimental animals and citrate removes the calcium ions which are vital for platelet function. Anticoagulation with heparin also interfered with platelet function, so that now, hirudins are the preferred anticoagulant. However it was observed that if, instead of stimulating platelet aggregation with adrenaline or ADP, serotonin was applied to the preparation, very little aggregation took place in spite of serotonin 5HT2A antagonists being the most potent inhibitors of thrombus growth in experimental animals. Another indicator that primary platelet agggregation is not a predictor of in vivo efficacy was the finding that 5HT2A antagonism inhibited aggregate growth. In a stenosed artery the platelets are activated by increased shear stress and blood turbulence with release of platelet serotonin causing positive feedback activation of more platelets. At present, there does not seem to be a bench in vitro test that accurately predicts in vivo efficacy in stenosed artery occlusive thrombosis.

Platelet Retention in Glass Bead Columns: Further Evidence for the Importance of ADP

Blood ◽  
1974 ◽  
Vol 44 (3) ◽  
pp. 411-425 ◽  
Author(s):  
V. J. McPherson ◽  
M. B. Zucker ◽  
N. M. Friedberg ◽  
P. L. Rifkin
Keyword(s):  
Platelet Aggregation ◽  
Acetylsalicylic Acid ◽  
Glass Bead ◽  
Room Temperature ◽  
Creatine Phosphokinase ◽  
Platelet Rich Plasma ◽  
Creatine Phosphate ◽  
Inhibitory Effect ◽  
Normal Platelet ◽  
Normal Individuals

Abstract Plasma of normal heparinized blood contained 0.284 µM ± SD 0.097 (ADP + ATP) with an ATP:ADP ratio of 2.5:1. Plasma from thrombocytopenic blood contained only 0.106 µM ± 0.073 (ADP + ATP). Blood with normal platelet retention released 0.234 µM ± 0.187 (ADP + ATP) during passage through a glass bead column, with an ATP:ADP ratio of 1.6:1. Significantly less was released in blood with low retention, i.e., samples from patients with von Willebrand’s disease, thrombasthenia, or thrombocytopenia, and some samples from normal individuals. Thus, nucleotides in the plasma of pre- and postcolumn blood appear to be derived from platelets; their release within glass bead columns is closely associated with normal platelet retention. Since release occurred at room temperature and was not prevented by acetylsalicylic acid or accompanied by measurable release of 14C-serotonin, the classic release reaction may not have been responsible. The low retention in platelet-rich plasma was variably increased by adding 0.5 µM ADP, an increase at least partly due to trapping of preformed aggregates. Retention in undisturbed blood was markedly inhibited by creatine phosphokinase with creatine phosphate (CPK-CP) and moderately inhibited by apyrase I (ATPase:ADPase 0.8:1) at an ADP-removing activity between 1 and 5 U/ml, indicating that ADP is essential for retention. At less than 1 U/ml, both apyrase I and II (ATPase: ADPase 2.8:1) enhanced retention in undisturbed blood, but CPK-CP was still inhibitory. These results suggest that enhancement is due to conversion of released ATP to ADP, as shown to occur in studies of platelet aggregation with ATP and ADP. At less than 1 U/ml, all three enzymes protected against the inhibitory effect of disturbance; this protection was marked with apyrase II, moderate with apyrase I and slight with CPK-CP. These observations provide additional evidence that ADP is responsible for the low retention caused by disturbance of the blood.

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