The Effect of Urea on Aggregation and Incubation Resistance of Human Platelets

1969 ◽  
Vol 21 (03) ◽  
pp. 403-408
Author(s):  
H Reuter ◽  
H Linker
Keyword(s):  
Platelet Rich Plasma ◽  
Divalent Cations ◽  
Human Platelets ◽  
Low Concentrations ◽  
Edta Plasma ◽  
Presence And Absence ◽  
High Concentrations ◽  
Induced Aggregation

SummaryInvestigations have been carried out to study the effect of urea on aggregation and incubation resistance of human platelets. Urea in high concentrations inhibits the Ca++-induced aggregation in platelet-rich EDTA-plasma while at low concentrations an increased aggregation takes place. Incubation of platelet-rich plasma at 37° C in the absence of divalent cations was performed in the presence and absence of 0.1 M urea. The temperature-induced percentage inhibition of aggregation was found to be significantly lower in the presence of urea.

scholarly journals Effects of a Polyoxyethylene Detergent on Platelet Function

1977 ◽  
Author(s):  
P.G. Barton
Keyword(s):  
Lactate Dehydrogenase ◽  
Platelet Rich Plasma ◽  
Secondary Phase ◽  
Human Platelets ◽  
Brij 58 ◽  
Low Concentrations ◽  
High Concentrations ◽  
Glass Surfaces ◽  
Induced Aggregation ◽  
Membrane Destabilization

Low concentrations of a polyoxyethylene detergent, Brij 58, inhibited the secondary phase of platelet aggregation induced by ADP in human citrated platelet rich plasma but had no effect on primary aggregation.Thrombin-induced aggregation of washed human platelets suspended in Tyrode’s buffer was inhibited after incubation of cells with 4.5 × 10-6M detergent. Development of prothrombin-converting activity and efflux of [14C]-serotonin, 45Ca2+ ions and labile endoperoxides were abolished concomitantly. Aggregation of washed platelets by collagen or sodium arachidonate and the attachment of cells to clean glass surfaces were also inhibited by the same concentration of Brij 58 that inhibited thrombin aggregation. This concentration of Brij 58 did not itself produce any release of a cytoplasmic marker, lactate dehydrogenase, from platelets. Higher concentrations of Brij 58, exceeding 10-4 M, lysed the cells liberating all of their serotonin, Ca2+ and lactate dehydrogenase. These results suggest that low concentrations of Brij 58 stabilize a membrane conformation against the action of platelet stimulatory agents while high concentrations produce membrane destabilization and cell lysis. The presence of albumin (BSA) in the suspending fluid increased by tenfold the concentrations of detergent required to “elicit these effects and this could be attributed to competitive binding of the detergent to albumin, demonstrated with [14C]-acetylated Brij 58.

HIGH CONCENTRATIONS OF HEPARIN ARE MORE INHIBITORY TO PLATE- AGGREGATION IN-VITRO THAN ARE LOW MOLECULAR WEIGHT HEPARINS AND HEPARINOIDS AT THE SAME CONCENTRATION

1987 ◽  
Author(s):  
H Messmore ◽  
B Griffin ◽  
J Seghatchian ◽  
E Coyne
Keyword(s):  
Molecular Weight ◽  
Heparan Sulfate ◽  
Dermatan Sulfate ◽  
Platelet Rich Plasma ◽  
Inhibitory Effect ◽  
Low Molecular Weight ◽  
Low Concentrations ◽  
High Concentrations ◽  
Induced Aggregation

Other investigators have shown that heparin in the usual therapeutic range (0.1-0.5 units/ml) has an enhancing effect on ADP aggregation and an inhibitory effect on collagen and thrombin induced aggregation. The effects of low molecular weight heparin (LMWH)and heparinoids (dermatan sulfate, heparan sulfate) on platelet aggregation have not been as extensivelystudied. We have utilized citrated platelet rich plasma (3.2%citrate-whole blood 1:9) drawn in plastic and adjusted to a final platelet count of 250,000/ul. A Bio-Data 4 channgl aggregometer was utilized with constantstirring at 37 C. The reaction was allowed to run for 20 minutes. Platelet rich plasma was supplemented 1:9 with saline or heparin and various agonists were then added ifno aggregation occurred. ADP, collagen, thrombin, ristocetin and serum from patients with heparin inudced thrombocytopenia (HIT) were utilized as agonists. Heparin was substituted at concentrations of 0.1 to 500 units per ml and various LMWH and heparinoids were substituted in equivalent anti-Xa or gravimetric concentrations. At low concentrations no inhibitory effect on any ofthe agonists was observed with any of the heparins or heparinoids. At concentrations of heparin of 100 u/ml or greater, all agonists were inhibited. At equivalent concentrations of five different LMWH (Cy 216, Cy 222, Pk 10169, Kabi 2165 and pentasaccharide) inhibition did notoccur at all or at very high concentions only. Dermatan sulfate and heparan sulfate inhibited only at high concentrations. HIT serum could not aggregate platelets with dermatan sulfate or pentasaccharide atany concentrations, but it was a good agonist with the other heparins and heparinoids.

Factors Influencing the Deaggregation of Human and Rabbit Platelets

1983 ◽  
Vol 49 (03) ◽  
pp. 162-167 ◽  
Author(s):  
R L Kinlough-Rathbone ◽  
J F Mustard ◽  
D W Perry ◽  
E Dejana ◽  
J-P Cazenave ◽  
...  
Keyword(s):  
Human Platelets ◽  
Release Reaction ◽  
Factors Influencing ◽  
Platelet Adherence ◽  
Activated Platelets ◽  
Fibrinogen Binding ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
Induced Aggregation

SummaryThe mechanisms involved in platelet deaggregation are unclear. Washed platelets from rabbits or humans aggregated by ADP can be deaggregated by EDTA or PGI2 if the release reaction has not occurred; during deaggregation 125I-fibrinogen dissociates from the platelets. Human platelets suspended in a medium without calcium undergo the release reaction during ADP-induced aggregation; EDTA, PGE, or PGI2 do not deaggregate these platelets although EDTA displaces much of the 125I-fibrinogen that associates with them during aggregation. Rabbit platelets aggregated by low concentrations of releaseinducing stimuli (sodium arachidonate, collagen or thrombin) can be deaggregated by EDTA, PGI2 or PGE1 and 125I-fibrinogen dissociates from them; with high concentrations of collagen or thrombin, deaggregation and dissociation of l25I-fibrinogen is slower. Human platelets that have undergone the release reaction in response to thrombin, collagen or a combination of sodium arachidonate and ADP are not readily deaggregated by EDTA or PGE1. Since aggregation and fibrinogen binding involving the glycoprotein IIb/IIIa complex are readily reversed by EDTA, and since Ca2+ is required for thrombospondin binding to activated platelets, there may be a third type of platelet-platelet adherence that is not disrupted by EDTA; this type of binding plays a greater role with human than with rabbit platelets.

Inhibition of Thrombin-, Epinephrine- and Collagen-Induced Platelet Aggregation by α1-Acid Glycoprotein

1979 ◽  
Author(s):  
P. Andersen ◽  
C. Eika
Keyword(s):  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Adenosine Diphosphate ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Clotting Time ◽  
Acid Glycoprotein ◽  
High Concentrations ◽  
Spontaneous Platelet Aggregation ◽  
Induced Aggregation

α1-Acid glycoprotein (α1,-acid GP) isolated from human plasma was found to inhibit thrombin-induced aggregation of washed human platelets (0.05 NIH U/ml final conc.), and inhibition was complete with physiological concentrations of α1-acid GP (1.0-1.5 g/1 final conc.). The inhibitory effect seemed to occur immediately on thrombin addition, thus similar to the effect of heparin previously observed. As opposed to heparin, however, α1-acid GP did not affect spontaneous platelet aggregation. Furthermore, α1-acid GP (in optimal cone.) reduced the combined inhibitory effect of heparin and antithrombin III on thrombin-induced platelet aggregation, thus consistent with the previous findings using heparin thrombin clotting time.Snyder and Coodley (1976) found α1-acid GP to inhibit platelet aggregation induced by epinephrine and adenosine diphosphate in platelet-rich plasma. As we also found α1-acid GP to inhibit collagen-induced platelet aggregation, α1-acid GP may possibly act as an inhibitor of the release reaction though fairly high concentrations (10 mg/ml final cone.) was needed for complete inhibition.

α, ω-Diadenosine Polyphosphates, a New Class of Substances, and ADP-Methylester Inhibit Platelet Aggregation and the Release Reaction

1975 ◽  
Author(s):  
R. Brossmer ◽  
M. J. Harrison ◽  
R. S. Goody
Keyword(s):  
Competitive Inhibition ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Diadenosine Polyphosphates ◽  
Release Reaction ◽  
Adp Release ◽  
Adenosine Derivatives ◽  
High Concentrations ◽  
Induced Aggregation ◽  
Phosphate Groups

A series of α, ω-diadenosine polyphosphates, which may be represented by the formula, where A = adenosine and n = the number of phosphate groups, were studied for their effect on the aggregation and release reaction of human platelets. The adenosine derivatives inhibit ADP-induced aggregation in the same order of efficiency as they inhibit the enzyme activity of adenylate kinase i. e. up to n = 5 the more phosphate groups, the more inhibitory the activity. Double reciprocal plots suggest that these adenosine derivatives act competitively with ADP. AP5A and AP4A inhibit the release reaction in washed platelets but AP3A and AP2A do so only in high concentrations. In platelet-rich plasma the APnA derivatives inhibit the ADP release reaction with diminished strength as n decreases from 5(55 ± 13% inhibition) to 2 (4±4% inhibition). The adenosine polyphosphates also inhibit the aggregation of washed platelets by thrombin and dextran sulphate but do not affect DEAE-Dextran aggregation.The ADP-methylester does not cause aggregation of platelets but inhibits ADP-induced aggregation and release in a manner suggestive of competitive inhibition.(Supported by “Deutsche Forschungsgemeinschaft, Bonn”, Sonderforschungsbereich 90, “Cardiovasculares System”.)

The Effect of Red Blood Cells on the ADP-induced Aggregation of Human Platelets in Flow Through Tubes

1990 ◽  
Vol 63 (01) ◽  
pp. 112-121 ◽  
Author(s):  
David N Bell ◽  
Samira Spain ◽  
Harry L Goldsmith
Keyword(s):  
Platelet Aggregation ◽  
Shear Rate ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Platelet Rich Plasma ◽  
Mean Transit Time ◽  
White Blood Cells ◽  
Aggregate Size ◽  
Human Platelets ◽  
Induced Aggregation

SummaryThe effect of red blood cells, rbc, and shear rate on the ADPinduced aggregation of platelets in whole blood, WB, flowing through polyethylene tubing was studied using a previously described technique (1). Effluent WB was collected into 0.5% glutaraldehyde and the red blood cells removed by centrifugation through Percoll. At 23°C the rate of single platelet aggregtion was upt to 9× greater in WB than previously found in platelet-rich plasma (2) at mean tube shear rates Ḡ = 41.9,335, and 1,920 s−1, and at both 0.2 and 1.0 µM ADP. At 0.2 pM ADP, the rate of aggregation was greatest at Ḡ = 41.9 s−1 over the first 1.7 s mean transit time through the flow tube, t, but decreased steadily with time. At Ḡ ≥335 s−1 the rate of aggregation increased between t = 1.7 and 8.6 s; however, aggregate size decreased with increasing shear rate. At 1.0 µM ADP, the initial rate of single platelet aggregation was still highest at Ḡ = 41.9 s1 where large aggregates up to several millimeters in diameter containing rbc formed by t = 43 s. At this ADP concentration, aggregate size was still limited at Ḡ ≥335 s−1 but the rate of single platelet aggregation was markedly greater than at 0.2 pM ADP. By t = 43 s, no single platelets remained and rbc were not incorporated into aggregates. Although aggregate size increased slowly, large aggregates eventually formed. White blood cells were not significantly incorporated into aggregates at any shear rate or ADP concentration. Since the present technique did not induce platelet thromboxane A2 formation or cause cell lysis, these experiments provide evidence for a purely mechanical effect of rbc in augmenting platelet aggregation in WB.

Properties of Washed Human Platelets

1977 ◽  
Vol 37 (02) ◽  
pp. 291-308 ◽  
Author(s):  
Raelene L Kinlough-Rathbone ◽  
J Fraser Mustard ◽  
Marian A Packham ◽  
Dennis W Perry ◽  
Hans-Joachim Reimers ◽  
...  
Keyword(s):  
Major Effect ◽  
Human Platelets ◽  
Immune Serum ◽  
Immune Serum Globulin ◽  
Serum Globulin ◽  
Platelet Adherence ◽  
Low Concentrations ◽  
Induced Aggregation ◽  
Extensive Release ◽  
Protein Free Medium

SummaryWe have shown previously that washed human platelets resuspended in Tyrode solution containing albumin and apyrase maintain their disc shape and their ability to aggregate upon the addition of low concentrations of ADP, providing fibrinogen is added to the suspending medium. We have now examined their responses to other aggregating and release-inducing agents. Collagen, arachidonate, thrombin, immune serum globulin, the ionophore A 23, 187 and phytohaemagglutinin from Phaseolus vulgaris caused aggregation and release of granule contents. The response to adrenaline was variable. Serotonin caused the platelets to change shape but no aggregation or release occurred. Addition of a small amount of plasma was necessary for ristocetin-induced aggregation. Polylysine caused immediate platelet-to-platelet adherence with little or no release of granule contents. Responses to collagen or thrombin were greater in a modified medium containing magnesium but no calcium; in this medium, aggregation caused by ADP or polylysine was followed by the release of granule contents whereas these agents caused aggregation without release in a medium with both calcium and magnesium. When protein was omitted from the suspending medium, platelet aggregation in response to ADP was variable. In this medium, collagen and thrombin caused more extensive release than in the albumin-containing medium. Aggregation by polylysine was accompanied by release and extensive lysis in the protein-free medium. Thus, the composition of the final resuspending medium has a major effect on the responses of washed human platelets to aggregating agents.

Effects of Halothane on Platelet Function

1980 ◽  
Vol 44 (03) ◽  
pp. 143-145 ◽  
Author(s):  
J Dalsgaard-Nielsen ◽  
J Gormsen
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Halothane Anaesthesia ◽  
Inhibition Of Platelet Aggregation ◽  
Transient Impairment ◽  
High Concentrations ◽  
Uptake And Release ◽  
Platelet Functions

SummaryHuman platelets in platelet rich plasma (PRP) incubated at 37° C with 0.3–2% halothane for 5–10 min lost the ability to aggregate with ADP, epinephrine and collagen.At the same time uptake and release of 14C-serotonin was inhibited. When halothane supply was removed, platelet functions rapidly returned to normal. However, after high concentrations of halothane, the inhibition of platelet aggregation was irreversible or only partially reversible.The results suggest that halothane anaesthesia produces a transient impairment of platelet function.

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.

The Action of an Aniline Derivative (AN 162) on Blood Coagulation and on Platelets

1971 ◽  
Vol 26 (01) ◽  
pp. 145-166
Author(s):  
E Deutsch ◽  
K Lechner ◽  
K Moser ◽  
L Stockinger
Keyword(s):  
Blood Coagulation ◽  
Citric Acid Cycle ◽  
Second Phase ◽  
Aniline Derivative ◽  
Acid Cycle ◽  
Enhancing Effect ◽  
Low Concentrations ◽  
Dual Action ◽  
High Concentrations ◽  
Induced Aggregation

Summary1. The aniline derivative AN 162, Donau Pharmazie, Linz, Austria, has a dual action on the blood coagulation: an anticoagulant and an coagulation enhancing effect.2. The anticoagulant action may only be demonstrated with high concentrations (over 1 X 10”3 M related to plasma) preferentially in PPP. It is partially caused by an inhibition of the endogenous way of generation of the prothrombin converting principle. In addition it is suggested that it interferes with the fibrinogen-fibrin reaction in a manner not yet understood.3. The coagulant action is caused by a greater availability of platelet constituents at low concentrations of AN 162 (over 1 × 10-4 M) and by the induction of a release reaction at higher concentrations. The platelet factors 3 and 4, serotonin, adenine, and acid phosphatase are released.4. AN 162 inhibits platelet aggregation. This inhibition can be demonstrated by the PAT of Breddin and in the stirred aggregation test of Born. It is more effective to inhibit the collagen-induced and the second phase of the adrenaline-induced aggregation than the ADP induced one. The platelet retention (test of Hellem) is also reduced.5. The action of AN 162 on the platelets is caused by a damage of the platelet membrane which becomes permeabel for both, soluble platelet constitutents and granula.6. AN 162 interferes with the energy metabolism of the platelets. It causes a loss of ATP, and inhibits the key-enzymes of glycolysis, citric acid cycle, fatty acid oxydation and glutathione reduction.7. AN 162 inhibits the growth of fibroblasts without influence on mitosis.

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