scholarly journals Intracellular mechanisms in the activation of human platelets by low-density lipoproteins

1987 ◽  
Vol 242 (2) ◽  
pp. 559-564 ◽  
Author(s):  
H E Andrews ◽  
J W Aitken ◽  
D G Hassall ◽  
V O Skinner ◽  
K R Bruckdorfer
Keyword(s):  
Arachidonic Acid ◽  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Low Density Lipoproteins ◽  
Low Density ◽  
Protein L ◽  
Stimulus Response ◽  
Dense Granules ◽  
Human Blood Platelets

Low-density lipoproteins (LDL) have been shown to cause aggregation of human blood platelets at concentrations above 2 g of protein/l. The secretion of the contents of platelet dense granules was detected, but not that of the lysosomes. LDL gave rise to a mobilization of [3H]arachidonic acid from phospholipids and the appearance of products of the cyclo-oxygenase pathway after only 10 s. LDL-promoted aggregation was inhibited by both aspirin and indomethacin. There was an increase in 3H-labelled diacylglycerols and the phosphorylation of 47 kDa proteins. LDL therefore shares at least some of the mechanisms of stimulus/response coupling with those of other agonists.

Tachyphylaxis in Human Blood Platelets Induced by Various Agonists and the Effect on Response To other Agonists

1979 ◽  
Author(s):  
P.A. Ruggles ◽  
M.C. Scrutton
Keyword(s):  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Thrombin Receptor ◽  
Common Pathway ◽  
Stimulus Response ◽  
Reversible Aggregation ◽  
Agonist Concentration ◽  
Subsequent Addition ◽  
Human Blood Platelets

Tachyphylaxis of human platelets to ADP, adrenaline, thrombin, 5-HT and vasopressin (VP) was induced by preincubation of stirred citrated PRP with an agonist concentration which induced primary reversible aggregation. The effect was demonstrable within 2 mins, after addition of some of the agonists and persisted for at least 30 mins. The extent of tachyphylaxis showed a positive correlation with agonist concentration used to induce the initial reversible response. Partial aganists at the ADP (2’, 3’-dialcohol ADP) or α-adreno-(clonidine) receptors did not induce significant tachyphylaxis to subsequent addition of the full agonist. In most instances platelets iaade tachyphylactic to a given agonist showed an unchanged or enhanced response to all other agonists including arachidonate. However tachyphylaxis to ADP, 5HT or thrombin was associated with an attenuated response to collagen. Furthermore tachyphylaxis to thrombin also caused attenuation of the response to VP and arachidonate. Induction of tachyphylaxis to VP, or addition of oxytocin (an inhibitor of aggregation induced by VP) had no effect on the response to thrombin. Thus the region of the thrombin receptor responsible for induction of tachyphylaxis to this agonist is not identical with that at which VP interacts. If stimulus-response coupling involves a common pathway for most agonists these data suggest that development of tachyphylaxis depends on events which preceed the effect of the agonists en this common pathway.

scholarly journals ULTRASTRUCTURAL LOCALIZATION OF Mg++-DEPENDENT DINITROPHENOL-STIMULATED ADENOSINE TRIPHOSPHATASE IN HUMAN BLOOD PLATELETS

1967 ◽  
Vol 15 (5) ◽  
pp. 267-272 ◽  
Author(s):  
VICTOR G. VETHAMANY ◽  
SYDNEY S. LAZARUS
Keyword(s):  
Enzyme Activity ◽  
Plasma Membrane ◽  
Human Blood ◽  
Adenosine Triphosphatase ◽  
Blood Platelets ◽  
Ultrastructural Localization ◽  
Human Platelets ◽  
Structural Localization ◽  
Adenosine Triphosphatase Activity ◽  
Human Blood Platelets

Fine structural localization of adenosine triphosphatase activity was studied in human platelets briefly fixed in cold formol calcium and then incubated in lead medium with added dinitrophenol. Under these conditions, the Mg++-dependent dinitrophenol-stimulated adenosine triphosphatase of platelet mitochondria was demonstrated, but neither granules nor plasma membrane showed enzyme activity.

scholarly journals Survival and recovery of human platelets stored for five days in a non- plasma medium

Blood ◽  
1986 ◽  
Vol 67 (3) ◽  
pp. 672-675 ◽  
Author(s):  
GA Adams ◽  
SD Swenson ◽  
G Rock
Keyword(s):  
Platelet Aggregation ◽  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Plasma Medium ◽  
Release Reaction ◽  
In Vivo Recovery ◽  
Human Blood Platelets

Abstract Human blood platelets were stored for five days as concentrates in 60 mL of: (a) plasma; (b) non-plasma medium with anticoagulant; and (c) non-plasma medium without anticoagulant. All preparations were equally functional when tested for platelet aggregation and release reaction in response to single agonist or synergistic pairs of agonists in vitro. Platelets stored in non-plasma medium with anti-coagulant had lower kallikrein, fibrino(gen)peptide A, lactate, and beta-thromboglobulin than did plasma controls after five days. In vivo recovery and survival of platelets stored in non-plasma medium with anticoagulant were 51.2% +/- 4.3% and 8.7 +/- 0.3 days, respectively, which were not statistically different from plasma controls of 39.2% +/- 4.9% and 7.2 +/- 0.8 days, respectively. It is concluded that platelets can be stored for five days in a non-plasma medium and still have good in vivo recoveries and survivals.

scholarly journals Accelerated uptake of 5-hydroxytryptamine by human blood platelets enriched in a sialic acid

1975 ◽  
Vol 148 (2) ◽  
pp. 335-336 ◽  
Author(s):  
L Szabados ◽  
L Mester ◽  
F Michal ◽  
G V R Born
Keyword(s):  
Sialic Acid ◽  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Acetylneuraminic Acid ◽  
Transport Receptor ◽  
Human Blood Platelets

The enzymically catalysed incorporation of N-acetylneuraminic acid into human platelets, whether suspended in their own citrated plasma or in buffered saline containing 0.17 mM-sucrose, accelerated the uptake of 5-hydroxytryptamine. This acceleration decreased with time. The observations may be explained by assuming that N-acetylneuraminic acid is a component of a transport receptor for 5-hydroxytryptamine.

Influence of Blood Platelets on Fibrinolysis

1961 ◽  
Vol 6 (02) ◽  
pp. 196-214 ◽  
Author(s):  
Rudolf Holemans ◽  
Rudolf Gross
Keyword(s):  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Bovine Blood ◽  
Platelet Surface ◽  
Inhibiting Effect ◽  
Platelet Concentration ◽  
Streptokinase Infusion ◽  
Human Plasminogen ◽  
Human Blood Platelets

Summary1. Human blood platelets contain a considerable amount of proactivator activity but no plasminogen activator activity or plasminogen. In test systems, containing streptokinase, the lysis of bovine fibrin is enhanced, depending upon the amount of platelets present.2. The platelet proactivator is completely destroyed by heating during 15 min at 70° C. Washing of platelets reduces their proactivator activity; however proactivator activity can still be found after ten washings.3. Bovine platelets do not contain proactivator activity. The similarity in the content in proactivator activity in plasma and platelets of both species, as well as the decrease of proactivator activity by washing, strongly suggests that the proactivator activity of human platelets is adsorbed on the platelet surface from the plasma.4. Both in human platelets and in bovine platelets, antifibrinolysin can be found. This factor is thermostable and is only slightly diminished by washing. The platelet antifibrinolysin seems for its larger part to be located in the platelets; only a small fraction may be adsorbed on their surface.5. The platelet antifibrinolytic activity can, depending upon the platelet concentration, be easily determined in systems containing urokinase or plasmin. Also in streptokinase-activated systems, bovine blood platelets have an inhibiting effect; human blood platelets inhibit streptokinase-induced fibrinolysis when their proactivator activity has been destroyed by heating. When streptokinase and unheated human blood platelets are tested on bovine fibrin the inhibitor effect is completely masked by the presence of proactivator.6. The clinical significance of these findings with regard to fibrinolysis occurring spontaneously or induced by streptokinase infusion, as well as their importance for the differentiation of proactivator and human plasminogen are discussed.

scholarly journals Short communication: possible association of newly absorbed serotonin with nonmetabolic, granule-located adenine nucleotides in human blood platelets

Blood ◽  
1975 ◽  
Vol 45 (3) ◽  
pp. 413-416
Author(s):  
H Holmsen ◽  
CA Setkowsky ◽  
HJ Day
Keyword(s):  
Guinea Pig ◽  
Human Blood ◽  
Short Communication ◽  
Adenine Nucleotides ◽  
Blood Platelets ◽  
Human Platelets ◽  
Serotonin Release ◽  
Release Reaction ◽  
Human Blood Platelets

[3H]-adenine-labeled human platelets in plasma were incubated with or without nonradioactive serotonin. Release reaction was then induced by ADP, epinephrine, collagen, or thrombin. Platelets that had been incubated with serotonin released four times as much serotonin as platelets incubated without serotonin. The specific radioactivities of the ATP and ADP released to plasma during release reaction induced with all four inducers were the same in both systems. This shows that when serotonin is taken up by human platelets, it enters the compartment containing nonmetabolic, granula-stored ATP, and not the compartment with metabolic extragranular ATP. These results suggest that the mechanism of serotonin storage in human platelets is similar to that in other species investigated, i.e., rabbit, guinea pig, and pig.

scholarly journals Survival and recovery of human platelets stored for five days in a non- plasma medium

Blood ◽  
1986 ◽  
Vol 67 (3) ◽  
pp. 672-675 ◽  
Author(s):  
GA Adams ◽  
SD Swenson ◽  
G Rock
Keyword(s):  
Platelet Aggregation ◽  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Plasma Medium ◽  
Release Reaction ◽  
In Vivo Recovery ◽  
Human Blood Platelets

Human blood platelets were stored for five days as concentrates in 60 mL of: (a) plasma; (b) non-plasma medium with anticoagulant; and (c) non-plasma medium without anticoagulant. All preparations were equally functional when tested for platelet aggregation and release reaction in response to single agonist or synergistic pairs of agonists in vitro. Platelets stored in non-plasma medium with anti-coagulant had lower kallikrein, fibrino(gen)peptide A, lactate, and beta-thromboglobulin than did plasma controls after five days. In vivo recovery and survival of platelets stored in non-plasma medium with anticoagulant were 51.2% +/- 4.3% and 8.7 +/- 0.3 days, respectively, which were not statistically different from plasma controls of 39.2% +/- 4.9% and 7.2 +/- 0.8 days, respectively. It is concluded that platelets can be stored for five days in a non-plasma medium and still have good in vivo recoveries and survivals.

Sign in / Sign up

Export Citation Format

Share Document