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

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.

Opposite Effect of Lysine on Platelet Aggregation Induced by Arachidonate and by Other Aggregants

10.1055/s-0038-1657221 ◽

1982 ◽

Vol 48 (01) ◽

pp. 078-083 ◽

Cited By ~ 3

Author(s):

C Ts'ao ◽

S J Hart ◽

D V Krajewski ◽

P G Sorensen

Keyword(s):

Platelet Aggregation ◽

Secondary Phase ◽

Aminocaproic Acid ◽

Adenosine Diphosphate ◽

Inhibitory Effect ◽

Human Platelets ◽

Primary Phase ◽

High Doses ◽

The Many ◽

SummaryEarlier, we found that ε-aminocaproic acid (EACA) inhibited human platelet aggregation induced by adenosine diphosphate (ADP) and collagen, but not aggregation by arachidonic acid (AA). Since EACA is structurally similar to lysine, yet these two agents exhibit vast difference in their antifibrinolytic activities, we chose to study the effect of lysine on platelet aggregation. We used L-lysine-HCl in these studies because of its high solubility in aqueous solutions while causing no change in pH when added to human plasma. With lysine, we repeatedly found inhibition of ADP-, collagen- and ristocetin-induced aggregation, but potentiation of AA-induced aggregation. Both the inhibitory and potentiation effects were dose-dependent. Low doses of lysine inhibited the secondary phase of aggregation; high doses of it also inhibited the primary phase of aggregation. Potentiation of AA-induced aggregation was accompanied by increased release of serotonin and formation of malondialdehyde. These effects were not confined to human platelets; rat platelets were similarly affected. Platelets, exposed to lysine and then washed and resuspended in an artificial medium not containing lysine, remained hypersensitive to AA, but no longer showed decreased aggregation by collagen. Comparing the effects of lysine with equimolar concentrations of sucrose, EACA, and α-amino-n-butyric acid, we attribute the potent inhibitory effect of lysine to either the excess positive charge or H+ and C1− ions. The -NH2 group on the α-carbon on lysine appears to be the determining factor for the potentiation effect; the effect seems to be exerted on the cyclooxygenase level of AA metabolism. Lysine and other chemicals with platelet-affecting properties similar to lysine may be used as a tool for the study of the many aspects of a platelet aggregation reaction.

Inhibition and potentiation of platelet function by lysolecithin

Blood ◽

10.1182/blood.v49.1.101.101 ◽

1977 ◽

Vol 49 (1) ◽

pp. 101-112 ◽

Cited By ~ 26

Author(s):

JH Joist ◽

G Dolezel ◽

MP Cucuianu ◽

EE Nishizawa ◽

JF Mustard

Keyword(s):

Platelet Function ◽

Platelet Rich Plasma ◽

Membrane Damage ◽

Adenosine Diphosphate ◽

Lactic Dehydrogenase ◽

Inhibitory Effect ◽

Human Platelets ◽

Serotonin Release ◽

Prolonged Incubation ◽

Abstract The effects of lysolecithin (LPC) on aggregation, serotonin release, shape, and lysis of rabbit, pig, or human platelets in platelet-rich plasma (PRP) or Tyrode albumin solution were examined during prolonged incubation. LPC added to citrated or heparinized PRP from humans or rabbits at a final concentration above 100 muM caused instantaneous inhibition of platelet aggregation induced by adenosine diphosphate (ADP), epinephrine (human PRP only), collagen, or thrombin. The inhibitory effect of LPC was found to be partially reversible over a period of 60–90 min. LPC at final concentrations above 30 muM also caused inhibition of ADP-, collagen-, and thrombin-induced aggregation and collagen- and thrombin-induced release of serotonin in suspensions of rabbit, pig, or human platelets. With washed platelets, the inhibitory effect not only rapidly disappeared but was followed by transient potentiation of aggregation and serotonin release. This potentiating effect of LPC was most pronounced when thrombin was used as stimulus. Both inhibition and potentiation were observed at concentrations of LPC that did not cause a significant change in platelet shape or loss from platelets of lactic dehydrogenase. Inhibition and potentiation were also observed when platelets were added to suspending medium containing LPC, although considerably higher concentrations of LPC were required under these conditions. Potentiation was not observed when LPC was added to citrated or heparinized rabbit or human PRP or to washed rabbit platelets suspended in a medium containing 4% bovine serum albumin. It seemed likely that some or all of the observed effects of LPC on platelet function were due to structural modification of the platelet membrane insufficient to result in gross membrane damage or platelet lysis. In addition, the results of experiments using 14C-LPC seemed to indicate that the observed potentiating effect of LPC on platelet function may be related to its rapid uptake and metabolism by the platelets.

The Effect of Tirofiban on Fibrinogen/Agonist-Induced Platelet Shape Change and Aggregation

Clinical and Applied Thrombosis/Hemostasis ◽

10.1177/1076029608316014 ◽

2008 ◽

Vol 14 (3) ◽

pp. 295-302 ◽

Cited By ~ 11

Author(s):

I. Anita Jagroop ◽

Dimitri P. Mikhailidis

Keyword(s):

Platelet Aggregation ◽

Platelet Activation ◽

Whole Blood ◽

Platelet Rich Plasma ◽

Shape Change ◽

Adenosine Diphosphate ◽

Vascular Events ◽

Spontaneous Platelet Aggregation ◽

Induced Aggregation ◽

Platelet Shape

There is evidence linking raised plasma fibrinogen (fib) and platelet hyperactivity with vascular events. One way to inhibit platelets is to block the platelet membrane glycoprotein (GP) IIb/IIIa receptor, which binds circulating fib or von Willebrand factor and cross-links platelets at the final common pathway to platelet aggregation. Tirofiban is a potent and specific fib receptor antagonist, used in the treatment of unstable angina. The authors assessed the effect of tirofiban on spontaneous platelet aggregation (SPA), fib-induced, serotonin (5HT)-induced, and adenosine diphosphate (ADP)-induced aggregation in whole blood by calculating the percentage free platelet count. These various agonists were used alone and in combination. The authors also measured the effect of tirofiban on agonists-induced (ADP, 5HT) platelet shape change (PSC). The effect of fib on PSC was also evaluated in platelet-rich plasma using a high-resolution (0.07 fL) channelyzer. Tirofiban significantly inhibited SPA, fib (2, 4, 8 g/L), ADP, ADP + fib combination, and 5HT-induced aggregation. Tirofiban had no effect on agonist-induced PSC. There was no apparent change in platelet volume with fib. In conclusion, tirofiban does not appear to have an effect on PSC, an early phase of platelet activation. Tirofiban seems to be a nonspecific and an effective inhibitor of platelet aggregation (a later phase of platelet activation) in whole blood. The clinical significance of these findings remains to be established.

PLATELET AGGREGATION DYNAMICS TO ADENOSINE DIPHOSPHATE IN NON-STIRRED SUSPENSIONS: LONG-RANGEINTERACTIONS FOR HUMAN, BUT NOT RABBIT, PLATELETS

10.1055/s-0038-1644464 ◽

1987 ◽

Author(s):

K Longmire ◽

M M Frojmovic

Keyword(s):

Platelet Aggregation ◽

Platelet Rich Plasma ◽

Linear Regression Analysis ◽

Time Lag ◽

Adenosine Diphosphate ◽

Human Platelets ◽

Dense Granule ◽

Second Phase ◽

Particle Count ◽

The simplest experimental approach for a theoretical description of platelet aggregation is based on kinetics of early multiplet formation (‹4 platelets per aggregate)occurring with diffusion-dependent particle collisions (no flow). The Smoluchowski theory was used to calculate collision efficiencies, αβ, from a linear plot of platelet particle count (Nt)−1 vs time (t) following addition of adenosine diphosphate (ADP) to citrated platelet-rich-plasma (PRP) for 7 human (H) and 2 rabbit (R) donors. A 0.1 ml sample of PRP was stirred with ADP for 0.5s, then immediately transferred to a 37°C bath for no-stir (diffusion) studies or further stirred with ADP for stir-induced aggregation studies. Samples were fixed with 0.5 ml 0.8% glutaraldehyde with particle count (Nt) determined with a resistive counter and % aggregation (PA) computed (reproducibility/sensitivity ‹ 5%). For stir conditions, R platelets were as sensitive and as rapidly aggregated by ADP (2-10 μM) as H platelets, with ∼ 1 s time lag for onset of PA. However, for no-stir conditions, linear regression analysis of data for ADP (5-10 μM) induced PA for H platelets for 0-30 s gave αβ = 7.5±4.6 (r = 0.9±0.05). Analysis at longer “diffusion” times showed a second phase (60-300 s) in some H donors with aB = 0.5±0.4 (4/9 donors), while R platelets showed only 1 phase with αβ = 0.65±0.15 (0-60 to 0-900 s) (r = 0.8±0.1). The ADP sensitivity ([ADP]½ corresponding to 50% of maximal changes) for the abnormally rapid PA in no stir H PRP for early times, measured over 0.4-100 μM range, was found to be ∼9 μM (5-17 μM range) and 3.5 μM (3-10 μM) for measurements respectively at 5-10 and 20-30s; these values were ∼ 3-8 × greater than lADPji measured for stirred suspensions for rate/extent of PA or rate of turbidometrically-measured macroaggregation (TA), while › [ADP] threshold for secondary aggregation in TA (10 H donors). These abnormally large aB values and their ADP sensitivity observed for human platelets are consistent with long-range interactions mediated by“chemotactic” agents released from the cells but distinct from normal dense granule release requiring macroaggregation, or by as yet uncharacterized membrane or polymetric bridges.

Effects of N-(2-Diethylaminoethyl)-N-(2-hydroxy- 2-phenylethyl)-2,5-dichloroaniline (AN 162) on Platelet Function and Blood Coagulation

Inhibition Of Platelet Aggregation

10.1055/s-0038-1653710 ◽

1971 ◽

Vol 26 (03) ◽

pp. 576-587

Author(s):

R. D Mac Kenzie ◽

T. R Blohm

Keyword(s):

Platelet Aggregation ◽

Blood Clotting ◽

Platelet Rich Plasma ◽

Adenosine Diphosphate ◽

Inhibitory Effect ◽

Clotting Time ◽

Clotting Factors ◽

Platelet Factor ◽

SummaryWhen AN 162 was added to human citrated platelet-rich plasma at 30-300 µg/ml, it inhibited platelet aggregation induced by adenosine diphosphate, collagen, and thrombin. When AN 162 was given orally to guinea pigs at 30 to 100 mg/kg, an in vivo inhibitory effect on platelet aggregability was found. Though it activated platelet factor 3, the concentration of AN 162 required for substantial activation was greater than that for inhibition of platelet aggregation. No effect on plasma clotting factors was found at or below 300 µg/ml. Slight prolongation of whole blood clotting time was found in the rat and monkey.

Inhibition and potentiation of platelet function by lysolecithin

Blood ◽

10.1182/blood.v49.1.101.bloodjournal491101 ◽

1977 ◽

Vol 49 (1) ◽

pp. 101-112

Author(s):

JH Joist ◽

G Dolezel ◽

MP Cucuianu ◽

EE Nishizawa ◽

JF Mustard

Keyword(s):

Platelet Function ◽

Platelet Rich Plasma ◽

Membrane Damage ◽

Adenosine Diphosphate ◽

Lactic Dehydrogenase ◽

Inhibitory Effect ◽

Human Platelets ◽

Serotonin Release ◽

Prolonged Incubation ◽

The effects of lysolecithin (LPC) on aggregation, serotonin release, shape, and lysis of rabbit, pig, or human platelets in platelet-rich plasma (PRP) or Tyrode albumin solution were examined during prolonged incubation. LPC added to citrated or heparinized PRP from humans or rabbits at a final concentration above 100 muM caused instantaneous inhibition of platelet aggregation induced by adenosine diphosphate (ADP), epinephrine (human PRP only), collagen, or thrombin. The inhibitory effect of LPC was found to be partially reversible over a period of 60–90 min. LPC at final concentrations above 30 muM also caused inhibition of ADP-, collagen-, and thrombin-induced aggregation and collagen- and thrombin-induced release of serotonin in suspensions of rabbit, pig, or human platelets. With washed platelets, the inhibitory effect not only rapidly disappeared but was followed by transient potentiation of aggregation and serotonin release. This potentiating effect of LPC was most pronounced when thrombin was used as stimulus. Both inhibition and potentiation were observed at concentrations of LPC that did not cause a significant change in platelet shape or loss from platelets of lactic dehydrogenase. Inhibition and potentiation were also observed when platelets were added to suspending medium containing LPC, although considerably higher concentrations of LPC were required under these conditions. Potentiation was not observed when LPC was added to citrated or heparinized rabbit or human PRP or to washed rabbit platelets suspended in a medium containing 4% bovine serum albumin. It seemed likely that some or all of the observed effects of LPC on platelet function were due to structural modification of the platelet membrane insufficient to result in gross membrane damage or platelet lysis. In addition, the results of experiments using 14C-LPC seemed to indicate that the observed potentiating effect of LPC on platelet function may be related to its rapid uptake and metabolism by the platelets.

Ticlopidine Facilitates the Deaggregation of Human Platelets Aggregated by Thrombin

10.1055/s-0038-1642389 ◽

1994 ◽

Vol 71 (01) ◽

pp. 091-094 ◽

Cited By ~ 15

Author(s):

M Cattaneo ◽

B Akkawat ◽

R L Kinlough-Rathbone ◽

M A Packham ◽

C Cimminiello ◽

...

Keyword(s):

Cardiovascular Disease ◽

Platelet Aggregation ◽

Prostaglandin E1 ◽

Human Platelet ◽

Adenosine Diphosphate ◽

Human Platelets ◽

Before And After ◽

Normal Human ◽

Platelet Aggregates ◽

SummaryNormal human platelets aggregated by thrombin undergo the release reaction and are not readily deaggregated by the combination of inhibitors hirudin, prostaglandin E1 (PGE1) and chymotrypsin. Released adenosine diphosphate (ADP) plays an important role in the stabilization of thrombin-induced human platelet aggregates. Since ticlopidine inhibits the platelet responses to ADP, we studied thrombin-induced aggregation and deaggregation of 14C-serotonin-labeled platelets from 12 patients with cardiovascular disease before and 7 days after the oral administration of ticlopidine, 250 mg b.i.d. Before and after ticlopidine, platelets stimulated with 1 U/ml thrombin aggregated, released about 80–90% 14C-serotinin and did not deaggregate spontaneously within 5 min from stimulation. Before ticlopidine, hirudin (5× the activity of thrombin) and PGE1 (10 μmol/1) plus chymotrypsin (10 U/ml) or plasmin (0.06 U/ml), added at the peak of platelet aggregation, caused slight or no platelet deaggregation. After ticlopidine, the extent of platelet deaggregation caused by the same inhibitors was significantly greater than before ticlopidine. The addition of ADP (10 μmol/1) to platelet suspensions 5 s after thrombin did not prevent the deaggregation of ticlopidine-treated platelets. Thus, ticlopidine facilitates the deaggregation of thrombin-induced human platelet aggregates, most probably because it inhibits the effects of ADP on platelets.

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

10.1055/s-0038-1645696 ◽

1990 ◽

Vol 63 (01) ◽

pp. 112-121 ◽

Cited By ~ 18

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 ◽

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.

Effects of Halothane on Platelet Function

10.1055/s-0038-1650105 ◽

1980 ◽

Vol 44 (03) ◽

pp. 143-145 ◽

Cited By ~ 19

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.

Inhibition of Platelet Function by Antiarrhythmic Drugs, Verapamil and Disopyramide

10.1055/s-0038-1657151 ◽

1982 ◽

Vol 47 (02) ◽

pp. 150-153 ◽

Cited By ~ 13

Author(s):

P Han ◽

C Boatwright ◽

N G Ardlie

Keyword(s):

Platelet Aggregation ◽

Platelet Function ◽

Antiarrhythmic Drugs ◽

Adenosine Diphosphate ◽

Inhibitory Effect ◽

Second Phase ◽

Ionophore A23187 ◽

High Concentrations ◽

Artery Disease

SummaryVarious cardiovascular drugs such as nitrates and propranolol, used in the treatment of coronary artery disease have been shown to have an antiplatelet effect. We have studied the in vitro effects of two antiarrhythmic drugs, verapamil and disopyramide, and have shown their inhibitory effect on platelet function. Verapamil, a calcium channel blocker, inhibited the second phase of platelet aggregation induced by adenosine diphosphate (ADP) and inhibited aggregation induced by collagen. Disopyramide similarly inhibited the second phase of platelet aggregation caused by ADP and aggregation induced by collagen. Either drug in synergism with propranolol inhibited ADP or collagen-induced platelet aggregation. Disopyramide at high concentrations inhibited arachidonic add whereas verapamil was without effect. Verapamil, but not disopyramide, inhibited aggregation induced by the ionophore A23187.