Dependence of Human Platelet Functional Responses on Divalent Cations: Aggregation and Secretion in Heparin- and Hirudin-Anticoagulated Platelet-Rich Plasma and the Effects of Chelating Agents

1981 ◽  
Vol 45 (02) ◽  
pp. 173-179 ◽  
Author(s):  
Bruce Lages ◽  
Harvey J Weiss
Keyword(s):  
Platelet Aggregation ◽  
Chelating Agents ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Divalent Cations ◽  
Normal Subjects ◽  
Concentration Addition ◽  
Functional Responses ◽  
Induced Aggregation

SummaryThe dependence of ADP- and epinephrine-induced platelet aggregation and secretion on extracellular divalent cations was examined by quantitating these responses in citrate-, heparin-, and hirudin-anticoagulated platelet-rich plasma. ADP-induced 14C-5HT secretion in heparin-PRP and hirudin-PRP was generally decreased, relative to that in citrate-PRP, without corresponding reductions in aggregation, whereas in response to epinephrine, both aggregation and secretion were decreased in heparin-PRP, and abolished in hirudin-PRP. In heparin-PRP, but not in hirudin-PRP, the degree to which these responses were altered was highly variable among normal subjects, and was dependent on the anticoagulant concentration. Addition of citrate restored the extent of ADP-induced secretion and of epinephrine-induced aggregation and secretion in heparin-PRP to that observed in citrate-PRP, and increased the extent of ADP-induced secretion in hirudin-PRP. Addition of EDTA or EGTA, however, had no effect on ADP-induced secretion in heparin-PRP. These results suggest that ADP-induced aggregation and secretion, as well as responses to ADP vs. epinephrine, have different dependencies on extracellular or surface-bound divalent cations. The variable responses observed in heparin-PRP may reflect direct interactions of heparin with platelets, and this variability may account for the conflicting results of previous studies.

Testosterone Potentiation of Ionophore and ADP Induced Platelet Aggregation : Relationship to Arachidonic Acid Metabolism

1981 ◽  
Vol 46 (02) ◽  
pp. 538-542 ◽  
Author(s):  
R Pilo ◽  
D Aharony ◽  
A Raz
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Unsaturated Fatty Acids ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Arachidonic Acid Metabolism ◽  
Ionophore A23187 ◽  
Low Concentrations ◽  
Induced Aggregation

SummaryThe role of arachidonic acid oxygenated products in human platelet aggregation induced by the ionophore A23187 was investigated. The ionophore produced an increased release of both saturated and unsaturated fatty acids and a concomitant increased formation of TxA2 and other arachidonate products. TxA2 (and possibly other cyclo oxygenase products) appears to have a significant role in ionophore-induced aggregation only when low concentrations (<1 μM) of the ionophore are employed.Testosterone added to rat or human platelet-rich plasma (PRP) was shown previously to potentiate platelet aggregation induced by ADP, adrenaline, collagen and arachidonic acid (1, 2). We show that testosterone also potentiates ionophore induced aggregation in washed platelets and in PRP. This potentiation was dose and time dependent and resulted from increased lipolysis and concomitant generation of TxA2 and other prostaglandin products. The testosterone potentiating effect was abolished by preincubation of the platelets with indomethacin.

Prostaglandins and Platelet Function in Diabetes

1979 ◽  
Author(s):  
J. García-Conde ◽  
J.A. Amado ◽  
J. Merino ◽  
I. Benet
Keyword(s):  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Normal Subjects ◽  
Inhibitory Effect ◽  
Rat Aorta ◽  
Diabetic Group ◽  
Diabetic Patients ◽  
Prostaglandin I2 ◽  
Induced Aggregation ◽  
Normal Controls

We have studied platelet aggregation induced by 0,5 mM. Araquidonic acid (AA) addition to platelet-rich-plasma (PRP) from 21 insulin treated diabetic patients and in 21 non-diabetic controls. The velocity of aggregation was significantly higher in the diabetic group. There was no differences in the velocity of aggregation in patients with or without retinopathy.The incubation of PRP of normal subjects at 37- during 5 minutes with 5,8 10-4 M. Imidazole changed the pattern of aggregation: The velocity of aggregation was slower and appeared a wave of disaggregation. Imida zole had not effect on aggregation in the diabetic group. This data add support to the findings published by COLWLLL showing that platelets from diabetics have hyperactive AA metabolism. Prostaglandin I2 (PGI2) obtained from rat aorta shows an inhibitory effect on ADP or AA induced aggregation. This effect is less marked in diabetic PRP than in PRP of normal controls. PGI2 release in platelet-poor-plasma from diabetics is normal. This can represent a resistance ot diabetic platelet to the anti aggregating effect of PGI 2. A similar finding was also appreciated with the PGE1 in three out of six patients so tar stu

Human Platelet Aggregation and Release Reaction Induced by Platelet Activating Factor (PAF-Acether) – Effects of Acetylsalicylic Acid and External Ionized Calcium

1985 ◽  
Vol 53 (02) ◽  
pp. 221-224 ◽  
Author(s):  
Marco Cattaneo ◽  
Maria Teresa Canciani ◽  
Pier Mannuccio Mannucci
Keyword(s):  
Platelet Aggregation ◽  
Acetylsalicylic Acid ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Normal Subjects ◽  
Human Platelet Aggregation ◽  
Low Concentrations ◽  
Before And After ◽  
Platelet Secretion

SummaryThe effects of the cyclo-oxygenase inhibition on PAF-acether- induced human platelet aggregation and secretion are controversial. We studied the above parameters on citrated platelet-rich plasma of 12 normal subjects before and after the in vivo administration of acetylsalicylic acid (ASA). Individual sensitivities to PAF-acether were highly variable. ASA completely inhibited the platelet secretion induced by low concentrations of PAF-acether, but caused only partial inhibition when platelets were exposed to high concentrations of PAF-acether. The concentration of PAF-acether which overcame the cyclo-oxygenase inhibition varied substantially, depending on the individual sensitivity of the platelets to it. The addition of CaCl2 2 mM to the samples did not affect the extent of the platelet secretion, but increased irreversible aggregation in samples taken both before and after the ASA administration. These data suggest that low concentrations of PAF-acether stimulate the human platelet secretion by activating the cyclo-oxygenase pathway, whereas higher concentrations also trigger other mechanism(s) that suffice to induce human platelet secretion and full aggregation.

scholarly journals Platelet Aggregation and Secretion: Effects of Anticoagulants and Divalent Cation Chelators

1977 ◽  
Author(s):  
B.A. Lages ◽  
H.J. Weiss
Keyword(s):  
Platelet Aggregation ◽  
Divalent Cation ◽  
Chelating Agents ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Concentration Addition ◽  
Single Wave ◽  
Cation Concentration ◽  
Aggregation Response ◽  
Low Levels

The aggregation and secretion responses of human platelets to ADP and epinephrine have been studied in citrated platelet-rich plasma (cPRP) and in heparinized platelet-rich plasma (hPRP) containing varying concentrations of divalent cation chelating agents. ADP induced a single wave of aggregation in hPRP while E induced biphasic aggregation in both hPRP and cPRP. Secretion of 14C-serotonin (5HT*) occurred in both hPRP and cPRP in response to ADP and E, but generally to a lesser extent in hPRP. The extent of 5HT* secretion in hPRP, relative to that in cPRP, decreased with increasing ADP concentration but remained essentially constant oyer the same range of E concentration. Addition of citrate or EDTA to hPRP produced a clear maximum in ADP-induced 5HT* secretion at levels of 5-20mM citrate or 2mM EDTA and, in some cases, was associated with the appearance of a biphasic aggregation response. With citrate, but not with EDTA, the chelator concentration corresponding to maximum secretion varied directly with the concentration of ADP. These results indicate that ADP-induced secretion is a function of divalent cation concentration but does not occur only at the low levels of divalent cation present in cPRP and that divalent cation may be more directly associated with ADP-platelet interactions than in interactions of platelets and E.

The Effect of Neuraminidase on Platelet Aggregation Induced by ADP, Norepinephrine, Collagen or Serotonin

1972 ◽  
Vol 28 (02) ◽  
pp. 221-227 ◽  
Author(s):  
James W. Davis ◽  
Kenneth T. N. Yue ◽  
Phyllis E. Phillips
Keyword(s):  
Platelet Aggregation ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Adenosine Diphosphate ◽  
Second Phase ◽  
Acetylneuraminic Acid ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Second Phases ◽  
Induced Aggregation

SummaryIncubation of human platelet-rich plasma (PRP) with neuraminidase enhanced platelet aggregation induced by adenosine diphosphate (ADP), norepinephrine, collagen or serotonin. Both first and second phases of ADP- and norepinephrine -induced aggregation were enhanced. In two plasmas a second phase of ADP-induced aggregation occurred after incubation with neuraminidase, but not in the control preparations. In one plasma a second phase of serotonin-induced platelet aggregation occurred after incubation with neuraminidase. The incubation of PRP with exogenous N-acetylneuraminic acid (a product of the action of neuraminidase) had no effect on platelet aggregation. A possible explanation of the observed enhancement of platelet aggregation by neuraminidase is that the enzyme may have released sialic acid from platelet membranes and thereby reduced their net negative surface charge.

Pharmacology Of 12-Deoxyphorbol Phenyl Acetate (12-DOPP) Induced Human Platelet Aggregation

1981 ◽  
Author(s):  
J Westwick ◽  
E M Williamson ◽  
F J Evans ◽  
V V Kakkor
Keyword(s):  
Platelet Aggregation ◽  
Human Platelet ◽  
Divalent Cations ◽  
Dienoic Acid ◽  
Free Radical Scavengers ◽  
Phenyl Acetate ◽  
Lipoxygenase Inhibitor ◽  
Human Platelet Aggregation ◽  
Induced Aggregation ◽  
Aggregation Of Platelets

12-DOPP (0.1 to 3.6µM) induced human platelet aggregation which was dependent upon the presence of divalent cations, intracellular level of C-AMP and an intact microtubular system in common with other aggregating agents. However, the small amount of platelet secretion and thromboxane (Tx) B2 synthesis did not contribute to 12-DOPP induced platelet aggregation as neither the Tx/endoperoxide antagonists pinane A2 (0.001-0.004mM) and trimethoquinone (0.01-0.1mM), the Tx synthesis inhibitors clotrimazole (0.1 to 0.8mM) and 9, 11, aza-prosta-5-13 dienoic acid (0.002-0.1) nor the cyclo-oxygenase inhibitor indomethacin (0.03-0.1mM) inhibited 12-DOPP induced aggregation. Furthermore the free radical scavengers aminopyrine (0.2-2.0mM), thioanisole (0.2-2.0mM) and butylated hydroxy toluene (0.07-1.4mM); the lipoxygenase inhibitor phenidone (0.5mM) and the leucotriene B and C antagonist FPL55712 (0.005-0.06mM) failed to modify 12-DOPP induced aggregation.However compounds which are thought to act as phospholipase inhibitors bromophenacyl bromide (0.3mM), mepracrine (0.20mM) and propanolol (0.2mM) were found to be effective inhibitors of 12-DOPP induced aggregation as well as the so- called calmodulin antagonists imipramine (0.12mM), desmethy- 1imipramine (0.033mM), promethazine (0.1mM) and trifluoperazine (0.35mM).The aggregation induced by 12-DOPP involves a direct effect upon platelets followed by the release of unknown substances probably phospholipids, which induce further aggregation of platelets.

13-Azaprostanoic Acid Potentiates Prostacyclin Induced Platelet Deaggregation

1981 ◽  
Author(s):  
L V Parise ◽  
D Venton ◽  
G C Le Breton
Keyword(s):  
Platelet Aggregation ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Present Report ◽  
The Other ◽  
Calcium Sequestration ◽  
Significant Difference ◽  
Induced Aggregation ◽  
Camp Levels ◽  
Stimulation Of

13-Azaprostanoic acid (13-APA), a specific thromboxane/endoperoxide receptor antagonist, reverses platelet aggregation stimulated by the endoperoxide analog U46619. The present report demonstrates that 13-APA also potentiates prostacyclin (PGI2) reversal of U46619-induced aggregation. Human platelet rich plasma was aggregated with 3 × 106M U46619. Deaggregation was induced 2 min. sitosequent to the addition of aggregating agent and was measured over a 3 min. period. Concentrations of 13-APA (4 × 10-4M) and PGI2(4 × 10-9M) were chosen such that each agent individually induced approximately 20% deaggregation. Addition of half of the above concentrations of these agents i.e. 2 × 10-4M 13-APA plus 2 × 10-9M PGI2resulted in 62% deaggregation, demonstrating that the observed response was supraadditive. Only 8% deaggregation was induced by 2 × 10-4M 13-APA alone and 0% by 2 × 10-9M PGI2 alone. PGI2 causes platelet deaggregation presumably through elevation of cAMP. 13-APA, however, did not increase cAMP levels even at concentrations of 13-APA as high as 1.2 × 10-3M i.e. 9.8 ± 1.3 pmoles/ml for control and 10.8 ± 1.2 for 13-APA. Nevertheless it is possible that the observed potentiation of deaggregation was the result of 13-APA facilitating PGI2 stimulation of adenylate cyclase. Measurement of cAMP during deaggregation, however, showed no significant difference between treatment with PGI2 alone and treatment with PGI2 plus 13-APA i.e. 11.3 ± 0.4 pmoles/ml for control, 11.4 ± 0.3 pmoles/ml for 13-APA, 16.1 ± 0.5 pmoles/ml for PGI2 and 16.5 ± 0.8 pmoles/ml for PGI2 plus 13-APA. These results clearly establish that 13-APA and PGI2deaggregate platelets by distinctly separate mechanisms. In this regard we propose that PGI2 causes platelet deaggregation by stimulating intraplatelet calcium sequestration through a cAMP dependent process. 13-APA, on the other hand, blocks the ability of U46619 to mobilize intraplatelet calcium. The combination of these two mechanisms presumably results in the observed potentiation of deaggregation.

scholarly journals The Effect of Imidazole on Human Platelet Aggregation

Blood ◽  
1971 ◽  
Vol 38 (4) ◽  
pp. 417-421 ◽  
Author(s):  
JAMES W. DAVIS ◽  
PHYLLIS E. PHILLIPS
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Glass Bead ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Second Phase ◽  
Platelet Function Tests ◽  
Human Platelet Aggregation ◽  
Function Tests ◽  
Induced Aggregation

Abstract Since imidazole buffers have been used in platelet function tests and the compound has been reported to alter several biochemical activities of platelets, it seemed important to determine whether imidazole influenced platelet aggregation. ADP-induced, collagen-induced, and norepinephrine-induced platelet aggregations were tested in platelet-rich plasma by turbidimetric techniques. Glass bead-induced platelet aggregation in whole blood was tested by a method dependent upon platelet counts. Imidazole, in concentrations of 5mM or less, inhibited aggregation induced by each of these four agents and had negligible effect on the pH of platelet-rich plasma. The second phase of both ADP- and norepinephrine-induced aggregation was inhibited or abolished by imidazole, and 5mM imidazole also inhibited the first phase of norepinephrine-induced aggregation. As little as 0.5 mM imidazole inhibited collagen-induced aggregation in some plasmas. Imidazole appears to be unsuitable for use as a buffer in platelet function tests.

Some Characteristics of Mouse Platelet Aggregation and a Comparison of the Activity of a Range of Compounds in Mouse and Human Platelet-Rich Plasma in Vitro

1981 ◽  
Vol 45 (01) ◽  
pp. 001-005 ◽  
Author(s):  
Barbara Nunn
Keyword(s):  
Platelet Aggregation ◽  
Prostaglandin E1 ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Similar Activity ◽  
Reversible Aggregation ◽  
Arachidonic Acid Metabolites ◽  
Acid Metabolites ◽  
Induced Aggregation

SummaryCollagen-induced platelet aggregation in mouse citrated platelet-rich plasma (PRP) was associated with 5-hydroxytryptamine (5-HT) release and degranulation. Adenosine 5’-diphosphate (ADP) induced monophasic and reversible aggregation with no degranulation. Mouse platelets gave no response to adrenaline but changed shape and sometimes aggregated in response to 5-HT. Both amines potentiated the effect of ADP. The respective potencies of prostaglandin E1, papaverine, VK 774, BL 3459 and adenosine as inhibitors of ADP-induced aggregation were similar in mouse and human PRP. Although ticlopidine had similar activity in the two species, aspirin and flurbiprofen were considerably less potent in mouse than human PRP as inhibitors of collagen-induced aggregation. It is suggested that collagen-induced aggregation of mouse platelets in vitro occurs by a mechanism largely independent of arachidonic acid metabolites.

scholarly journals Studies on Ristocetin Induced Platelet Aggregation

1977 ◽  
Author(s):  
R.L. Nachman ◽  
E.A. Jaffe ◽  
B.B. Weksler
Keyword(s):  
Platelet Aggregation ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Membrane Surface ◽  
Surface Protein ◽  
Human Platelets ◽  
Glycoprotein I ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

Human platelets washed and fixed in paraformaldehyde aggregate in the presence of the antibiotic ristocetin and normal plasma. This aggregation response is abolished after digestion of the fixed platelets with chymotrypsin. Antisera to fixed washed platelets were produced in rabbits and absorbed with chymotrypsin-treated, fixed washed platelets. Monovalent Fab fragments obtained from the isolated γ-globulin fractions of the antisera blocked ristocetin-induced aggregation of fixed washed platelets in buffer and normal platelets in platelet-rich plasma. By double-antibody immunoprecipitation, it was shown that the antibody which blocked the ristocetin reaction interacted with a platelet membrane surface protein of mol.wt.155,000. Partially purified preparations of membrane glycoprotein I obtained from wheat germ affinity columns block the ristocetin reaction. The results suggest that the glycoprotein I complex on the surface of the human platelet mediates ristocetin-induced von Willebrand factor-dependent platelet aggregation.

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