scholarly journals The Role of Whole Blood Platelet Aggregation Studies in the Diagnosis of Unexplained Bleeding Tendencies

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2260-2260
Author(s):  
Nicole De Simone ◽  
Ravi Sarode ◽  
Sean Yates ◽  
Karen Matevosyan ◽  
Manasa Reddy ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Selective Serotonin ◽  
Impedance Method ◽  
Platelet Dysfunction ◽  
Atp Secretion ◽  
Abnormal Results

Abstract Introduction: Platelet aggregation studies (PAS) are an important and underutilized diagnostic test (due to non-availability in most clinical laboratories and the requirement to be performed within 4 hours of sample collection) used in the evaluation of unexplained mucocutaneous type of bleeding after ruling out von Willebrand disease. Platelet aggregation studies are typically performed by one of two methods: impedance method using whole blood aggregometry (WBA) and light transmission aggregometry (LTA) using platelet rich plasma (PRP). WBA confers several advantages over LTA. First, it does not require centrifugation, which not only reduces testing time by half, but also avoids platelet activation and loss of giant thrombocytes. Second, in vivo conditions are better replicated reflecting the natural milieu including red and white blood cells, which are known to affect platelet function in vivo. In addition, WBA requires smaller blood volume making testing feasible for neonates and pediatric patients. Lastly, simultaneous assessment of platelet ATP release is performed to assess secretion defects. Despite these advantages, WBA is not commonly used. Aims: To analyze our data to further support the diagnostic utility of WBA in identifying platelet dysfunction as the etiology of bleeding tendencies. Methods: A retrospective chart review of patients on whom PAS were performed between June 2011 and September 2014. Results: We performed 202 PAS on 162 patients. 82% of patients were females and the average age was 28 years (range 9 months-87 years). 24 (15%) patients were pediatric (range 9 months-18 years). 83 of 162 (51%) patients had abnormal results (52% of adults and 50% of the pediatric cases). 26 of the 162 (16%) patients had repeat studies performed. Of these patients, 77% (20/26) had reproducible findings that confirmed the previous results. 8% (2/26) had normalized platelet function after discontinuation of medications (e.g. statins, fish oil, selective serotonin reuptake inhibitor) known to induce platelet dysfunction. 15% (4/26) had different responses to agonists on repeat testing. Abnormal WBA studies revealed decreased to absent responses to various agonists described in table 1. In patients on selective serotonin release inhibitors (SSRIs), there was a spectrum of responses to agonists; the most common abnormality was global dysfunction. Abnormalities to single agonists, such as ADP and AA, were also seen in patients taking SSRIs. Non-steroidal anti-inflammatory drugs affected aggregation with arachidonic acid (AA) and AA+ADP. Statins affected aggregation with AA alone, AA+ADP and AA+ATP secretion. 3 patients had platelet dysfunction consistent with Acquired Glanzmann's Syndrome due possibly to autoantibodies in the setting of chronic lymphocytic leukemia. Conclusion: Over 50% patients tested by WBA had abnormal platelet function giving high positive predictive value for this test in a selected group of patients who otherwise would have carried a non-specific bleeding diagnosis with non-specific treatment. Table 1. Distribution of Agonists Eliciting Impaired Responses Agonists Eliciting Impaired Response Number of Studies with Abnormal Results AA+Collagen (Aspirin like defect) 27 (23%) AA+Collagen+ADP 22 (18%) AA+ADP 21 (17%) AA+Collagen+ADP+Ristocetin (Global dysfunction) 19 (15%) ADP 11 (9%) AA 7 (6%) ADP+Collagen 4 (3%) AA+ADP+Ristocetin 3 (2%) Decreased ATP Secretion 8 (7%) AA=Arachidonic Acid Disclosures No relevant conflicts of interest to declare.

Dasatinib-Induced Platelet Dysfunction.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2941-2941 ◽  
Author(s):  
Alfonso Quintas-Cardama ◽  
Xin Han ◽  
Hagop Kantarjian ◽  
Jorge Cortes
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Function Analysis ◽  
Chronic Phase ◽  
Myelogenous Leukemia ◽  
Light Transmittance ◽  
P Value ◽  
Platelet Dysfunction

Abstract Dasatinib is efficacious and safe in patients (pts) with chronic myelogenous leukemia (CML) after imatinib failure. However, dasatinib therapy has been linked to bleeding in some pts, typically affecting mucosal surfaces. We analyzed the effect of dasatinib on basic coagulation tests and platelet aggregation function in 55 pts with CML in chronic phase at diagnosis (1), >8 weeks after tyrosine kinase inhibitor (TKI) discontinuation (3), or during therapy with the ABL/SRC inhibitors dasatinib (n=27) and bosutinib (n=12), or the aminopyrimidine derivatives imatinib (n=8) and nilotinib (n=4). Median age was 54 yrs (range, 22–80), WBC 5.5 ×109/L (range, 2.1–58.5), hemoglobin 12.2 g/dL (range, 9.7–15.1), and platelets 230 ×109/L (range, 80–746). Only 2 pts (both on imatinib and warfarin) had abnormal basic coagulation parameters (prolonged prothrombin time [PT]). In the remainder 53 pts, the median PT time was 11.6 sec (9.8–13), activated partial thromboplastin time (aPTT) 28.5 sec (range, 21–33.9), and fibrinogen level 495 mg/dL (range, 336–700), suggesting an intact secondary hemostasis. To evaluate the primary hemostasis status, platelet aggregation was measured by turbidometry in 1 mL of platelet-rich plasma upon stimulation with 5 μM of ADP, 1 μg/ml of collagen, 1 μM of epinephrine, 1 mM arachidonic acid, or 8 μL of ristocetin by using a Whole Blood Lumi-Aggregometer (Chrono-Log Corporation, Havertown, PA). Aggregation was expressed as the maximal percent change in light transmittance from baseline using platelet-poor plasma as a reference. Five (9%) patients (2 bosutinib, 1 nilotinib, and 2 imatinib) were on aspirin and showed an aspirin-like effect (decreased platelet aggregation with arachidonic acid [AA] and epinephrine [Epi]). Patients off-TKI or untreated had a normal platelet aggregation test. Results on the remaining 46 assessable patients demonstrate that dasatinib is strongly associated platelet aggregation defects, particularly an aspirin-like effect, when compared with other TKIs. Platelet function analysis by PFA-100 showed that addition of dasatinib (400 nM) to fresh whole blood obtained from a healthy volunteer rapidly induced platelet dysfunction. Closure times were prolonged from 100 sec (baseline) to >300 sec in response to Epi (normal <160 sec) but not in response to ADP (from 72 to 84 sec, normal <120 sec) after 30 min incubation. In summary, our data indicate that dasatinib does not interfere with secondary hemostasis. Rather, it inhibits platelet function in an aspirin-like manner. This effect, while independent, can be additive to dasatinib-induced thrombocytopenia and may account for the bleeding diathesis observed in pts with CML receiving dasatinib. Table 1. Effect of BCR-ABL kinase inhibitors on platelet aggregation Dasatinib Bosutinib Nilotinib or Imatinib Platelet aggregation test n=27 n=10 n=9 p value Normal (%) 4 (15) 8 (80) 6 (67) < 0.01 Abnormal (%) 23 (85) 2 (20) 3 (33) < 0.006 Only with Epi 7 1 0 With both Epi and AA 14 1 3 With all agonists 2 0 0

Rapid Assessment of Platelet Function Using Thromboelastography and Small Volumes of Citrated Whole Blood.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3995-3995 ◽  
Author(s):  
Fred G. Pluthero ◽  
Margaret L. Rand ◽  
Victor S. Blanchette ◽  
Walter H. Kahr
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Function Analysis ◽  
Maximum Amplitude ◽  
Ease Of Use ◽  
Platelet Response ◽  
Platelet Function Disorders ◽  
Wide Range

Abstract Platelet function disorders are a key cause of abnormal bleeding, and diagnosis is challenging because: platelet abnormalities are diverse, affecting many aspects of function; variability in platelet function testing in clinical laboratories makes it difficult to compare results; large blood volumes required for platelet function analysis make it difficult to perform in neonatal patients; manipulation of platelet rich plasma used for platelet aggregation can lead to test variability; platelet aggregation curves are difficult to interpret in thrombocytopenic patients. We describe a method of testing platelet function using citrated whole blood and thromboelastography (TEG) that overcomes some of these limitations. Commercially-available platelet mapping kits allow the effects of the platelet agonists adenosine diphosphate (ADP) and arachidonic acid (AA) to be assessed via a TEG assay where reptilase and activated factor XIII produce fibrin clots independent of thrombin in heparinized whole blood. The activation and aggregation of platelets is quantified by measuring the difference in maximum amplitude (MA) between unstimulated samples, which form weak fibrin-only clots, and samples with agonists added, which form stronger clots containing fibrin and activated/aggregated platelets. Platelet mapping was used as the basis for a TEG assay which can be used to assess platelet responses to a wide range of stimuli - including ADP, AA, epinephrine, collagen, U46619 (thromboxane-A2 receptor agonist), SFLLRN (PAR-1 thrombin receptor activating peptide) and AYPGKF (PAR-4 activating peptide) - in small samples (330μL) of citrated native (CN) blood or plasma to which heparin is added to a concentration of 20U/mL. Samples were recalcified by adding calcium chloride to 10mM (necessary for the function of reptilase and FXIIIa), and other reagent volumes were the same as in platelet mapping assays, with fibrin activator prepared at 1/2 regular strength. The concentrations of platelet agonists were: collagen 51μg/ml, epinephrine 0.27μM, ADP 5.4μM, arachidonic acid 135μg/mL, U46619 2.6μM, SFLLRN 6.76μM and AYPGKF 34μM. These concentrations produced TEG MA values in heparinated fibrin-activated CN blood from a panel of normal individuals comparable to those obtained from recalcified CN blood in the absence of heparin (the fibrin/platelet response control). The platelet response was rapid with maximum amplitudes reached within 10 minutes for all agonists except collagen, which required &gt;30 minutes to produce maximum amplitude. We have found this TEG platelet-response assay to be useful in detecting platelet function abnormalities, producing results which correlate with and extend those of other platelet function tests. For example in one patient a weak response to epinephrine corresponded to similar platelet aggregation results, and in another the TEG assay detected a weak PAR-1 response not specifically detected in other tests. The assay has also proven useful in assessing platelet function in blood and plasma having low platelet concentrations (&lt;50 x 10E9/L) from experimental or pathological causes (e.g. thrombocytopenia), in titrating platelet responses to agonists and in assessing the effects of antiplatelet agents in vivo and in vitro. Thus this TEG platelet function assay has the advantages of speed, ease of use, flexibility, adaptability to low platelet concentrations and sample economy, requiring small volumes of citrated blood which can be used for other coagulation assays and platelet response tests.

Comparison of Rapid Platelet Function Assay with Whole Blood Platelet Impedance Aggregometry for the Definition of Aspirin Resistance.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4018-4018
Author(s):  
Anna M. Dyszkiewicz-Korpanty ◽  
Anne Kim ◽  
James D. Burner ◽  
Eugene P. Frenkel ◽  
Ravindra Sarode
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Blood Platelet ◽  
Aspirin Resistance ◽  
Impedance Aggregometry ◽  
Definition Of ◽  
Induced Aggregation

Abstract The reported incidence of aspirin (ASA) resistance ranges from 5 to 30%. Various platelet function assays have been employed to detect aspirin resistance in patients with cardio- and cerebrovascular disease. Such a high proposed incidence of ASA resistance poses a critical need for a rapid point-of -care (POC) platelet function test. Unfortunately, no uniformly accepted definition of ASA resistance exists. Platelet aggregation studies that have been used to define ASA resistance are time consuming and require special technical expertise. The Ultegra Rapid Platelet Function -ASA (RPFA-ASA) has been developed as a POC test that is performed without sample processing. This optical method measures agglutination of fibrinogen-coated beads upon platelet activation with arachidonic acid. In the presence of aspirin effect, however, the agglutination of the beads is inhibited. The described cutoff of ≥ 550 Aspirin Reaction Units (ARU) is termed non-responsiveness to ASA based on a preclinical study and subsequent correlation with epinephrine-induced platelet aggregation in platelet rich plasma. Since RPFA-ASA uses whole blood, we validated its performance characteristics against a classic whole blood platelet aggregation assay (WBA). We studied 50 healthy volunteers, aged 25–75 (24 men, 26 women) with normal CBC, who had not ingested anti-platelet drugs for 14 days prior to the study. Baseline studies included WBA (dual channel aggregometer, Chrono-log Inc., Havertown, PA) using both arachidonic acid (AA -0.5; 0.25 mM) and collagen (1; 2 μg/mL) as well as an RPFA-ASA assay (Accumetrics Inc., San Diego, CA). These studies were repeated after 3 days of ASA (325 mg/d) intake. Based on a review of the literature, we defined an adequate ASA response as a completely inhibited AA-induced platelet aggregation and at least 30% inhibition of collagen-induced aggregation (both concentrations of the agonist). Thus, those with &lt; 30% inhibition of aggregation response to collagen were considered ASA resistant. Eleven subjects were ASA resistant by WBA (20%; 8 females and 3 males (aged 25–63). In contrast, since all 50 subjects achieved ARU values of &lt; 550 ARU, none were recognized as an ASA non-responder by the RPFA-ASA. While the current cutoff of &lt; 550 ARU posed by the Ultegra RPFA-ASA does identify those who have taken ASA, the assay is unable to recognize ASA non-responders. Thus, based on these data, the appropriate cutoff for the recognition of ASA resistance by the RPFA-ASA should be re-adjusted to a significantly lower level to ensure appropriate assay results.

An Anti-Phosphatidylserine (PS) Antibody, Tarvacin™ That Targets Tumor Blood Vessels Does Not Affect Platelet Function In Vitro.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3950-3950
Author(s):  
Anna M. Dyszkiewicz-Korpanty ◽  
Ravindra Sarode ◽  
Philip E. Thorpe ◽  
Eugene P. Frenkel
Keyword(s):  
Endothelial Cells ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Platelet Function ◽  
Whole Blood ◽  
Impedance Method ◽  
Type I ◽  
Tumor Vessels ◽  
Glycoprotein I

Abstract Tarvacin™ is a chimeric anti-PS antibody that is currently in Phase I clinical trials in cancer patients. It acts by targeting PS that becomes exposed on vascular endothelium in tumors in response to oxidative stress in the tumor microenvironment. Tarvacin™ recognizes a complex of PS and the PS-binding protein, β2 glycoprotein I. Host leukocytes are induced to bind to the complex in tumor vessels and destroy tumor vessels by antibody-dependent cellular cytotoxity. However, antibodies directed against PS-associated proteins are also known to elicit anti-phospholipid syndromes (APS). Anti-PS antibodies possibly cause APS by displacing anticoagulant proteins from PS on activated cell or by enhancing the binding of prothrombin; another explanation might be a direct activation of endothelial cells and platelets. The aim of the study was to determine whether Tarvacin ™ induces or interferes with platelet activation caused by ADP, collagen type I or calcimycin in vitro. Blood was drawn from 3 healthy volunteers, aged 31–54, who have not taken any antiplatelet medication for 14 days prior to the study. Dual channel whole blood aggregometer (Chronolog, Havertown, PA, USA) was employed for platelet aggregation studies in whole blood (WB/impedance method) and platelet rich plasma (PRP/optical method). Platelet count in PRP was adjusted to 200 K/μL. Platelet agonists (PS exposure triggers) used in the experiments were as follows: collagen (0.5, 1, 2 μg/mL), ADP (1.25, 2.5, 5, 10 μM), Calcimycin (10, 20, 30 μM) and Calcium ions (1, 2 mmol/L). Tarvacin™ was provided by Peregrine Pharmaceuticals Inc, Tustin, CA. The Anti-CD 20 antibody, Rituxan ™ and physiologic saline were used as controls. Specimens (WB diluted with saline in 1:1 ratio or PRP) with the addition of Tarvacin™ (100 μg/mL) or Rituxan ™ (100 μg/mL) or saline were first incubated on a gentle mixer for 10 minutes; incubation was then continued at 37 ° in the aggregometer well for another 5 minutes. Agonist-induced platelet aggregation was subsequently examined. Platelet aggregation studies in both WB and PRP showed that Tarvacin™ neither induced platelet activation, nor inhibited platelet activation in response to ADP, collagen or calcimycin in vitro. In conclusion, Tarvacin™ does not affect platelet function in the present in vitro assays. Possibly, the epitope on the PS -β2 glycoprotein I complex does not orientate the antibody in a manner that interferes with platelet activation. Alternatively, activated endothelial cells or other factors may be critical to support platelet activation.

Hypoxia Reoxygenation Treatment Induces Platelet Hyperactivity and Relieves Calpain-1-Mediated Inhibition of Platelet Aggregation in a Mouse Model of Severe Sickle Cell Disease

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 413-413
Author(s):  
Jennifer O. Nwankwo ◽  
Rod R. Warburton ◽  
Thomas Gremmel ◽  
Anja J. Gerrits ◽  
Lauren J. Richey ◽  
...  
Keyword(s):  
Steady State ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Sickle Cell ◽  
Whole Blood ◽  
Research Funding ◽  
Blood Platelet ◽  
Platelet Dysfunction ◽  
Inhibition Of Platelet Aggregation

Abstract Introduction: With an estimated 15 million patients and no drug that addresses its etiology, sickle cell disease (SCD) remains an area of unmet need. Vaso-occlusive pain crisis (VOPC), the hallmark of SCD, is initiated by sickle RBCs (sRBCs) recruiting leukocytes and platelets to potentiate vessel occlusion. ADP released by sRBCs is a potent activator of platelets, and sickle cell patients are known to have activated platelets in circulation both at steady state and during VOPC. However, the mechanism underlying platelet dysfunction in SCD is not fully understood. Platelet activation mediated by the protease activated receptors (PAR1 and PAR4 in humans, PAR3 and PAR4 in mice), triggers PLC-β activation resulting in calcium mobilization. The increased calcium flux leads to activation of GPIIbIIIa/aIIbb3, GP1b, and P-selectin involved in platelet aggregation, adhesion, and rolling. Prior evidence has established a role of the calcium-activated cysteine protease, calpain-1 in platelet activation. Washed platelets from calpain-1 knockout C57BL/6 mice demonstrated impaired platelet aggregation. However, due to the critical contribution of sRBCs to platelet dysfunction in SCD, whole blood (impedance) aggregometry represents a physiological assessment of platelet aggregation. Methods: Townes SCD mice (SS) were backcrossed with calpain-1 knockout (CKO) mice to generate SCD mice lacking calpain-1 (SSCKO). Humanized mice (AA) were used as controls. Using flow cytometry, we evaluated in vivo platelet activation following stimulation with ADP and Thrombin GPRP. Platelet counts were obtained via ADVIA 120 and flow cytometry. For platelet aggregation, 500 μL of blood was harvested from the vena cava of AA, SS, SSCKO, and CKO mice. Whole blood aggregation in response to PAR4 stimulation was assessed using the Roche Multiplate Analyzer. A separate group of mice were challenged with hypoxia/reoxygenation (H/R) treatment (3 hours of 10.5% O2, followed by 4 hours of 21% O2) prior to platelet aggregation testing. SCD mice are characterized by tissue infarcts suggestive of thrombus formation. To examine whether H/R treatment induces formation of fibrin thrombi, we harvested brain, lungs, heart, kidneys, liver, and spleen following blood collection, and performed histology. Results: Compared to AA, SS and SSCKO mice are thrombocytopenic. Similar to Berkeley, Townes mouse platelets are activated in vivo, demonstrated by activated GPIIbIIIa on circulating platelets. At steady state, PAR4 agonist-induced platelet aggregation is similar in AA and SS mice (64 U v. 53 U, n = 6-10/group, p = 0.3). As depicted in Fig 1., SSCKO mice show significantly reduced platelet aggregation compared to SS mice (13 U v 53 U, p<0.001, n = 6-10 per group). As expected, H/R treatment induces platelet hyperactivity in SS, but not AA mice (71 U v. 59 U, p = 0.04, n = 6/group). Interestingly, the H/R-induced platelet hyperactivity partially relieves the calpain-1-mediated inhibition of platelet aggregation in SSCKO mice at steady state (Fig 2) (53 U v. 13 U, p<0.001, n = 6-8/group). Furthermore, CKO mice do not show defective platelet aggregation at both steady state, and following H/R treatment, indicating an important role for sRBCs and adhesion in whole blood aggregation. Despite attenuated platelet aggregation, SSCKO platelets at steady state show comparable expression of activated GPIIbIIIa relative to their AA and SS counterparts, indicating that the impaired aggregation at steady state is not due to defective integrin translocation. Since the Roche Multiplate Analyzer takes platelet adhesion into account in determining aggregation, we hypothesize that defective SSCKO whole blood aggregation at steady state is due to reduced cell adhesion. Finally, while silent infarcts were detected in all tissues, fibrin thrombi were not detected, a finding consistent with studies in the Berkeley model reporting minimal thrombi formation in tissues. In summary, we report that calpain-1 is required for platelet aggregation in steady state SCD but not following H/R treatment. This is the first study of H/R-induced platelet dysfunction in the Townes model, and raises the possibility of targeting calpain-1 as a treatment for platelet hyperactivity in SCD. Figure 1. Impaired steady state whole blood platelet aggregation in SSCKO mice (panel 3). Figure 1. Impaired steady state whole blood platelet aggregation in SSCKO mice (panel 3). Figure 2. H/R relieves calpain-1-mediated inhibition of platelet aggregation in SS-CKO mice (panel 3). Figure 2. H/R relieves calpain-1-mediated inhibition of platelet aggregation in SS-CKO mice (panel 3). Disclosures Jakubowski: Eli Lilly and Company: Employment, Equity Ownership. Frelinger:GL Synthesis: Research Funding; Celerion: Research Funding; Megakaryon: Research Funding; Bristol-Myers Squibb: Research Funding; Sysmex: Research Funding; Eisai: Research Funding; Baxalta: Research Funding; Pfizer: Research Funding; GE Global Research: Research Funding; NIH: Research Funding.

Effect of Aspirin Infusions on Platelet Function in Humans

1990 ◽  
Vol 79 (1) ◽  
pp. 37-42 ◽  
Author(s):  
K. M. Wilson ◽  
D. M. Siebert ◽  
E. M. Duncan ◽  
A. A. Somogyi ◽  
J. V. Lloyd ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Blood Coagulation ◽  
Platelet Function ◽  
Whole Blood ◽  
Dependent Manner ◽  
Inhibitory Effects ◽  
Concentration Dependent Manner ◽  
Infusion Period

1. The inhibitory effects of aspirin on platelet function in vitro have been shown to be both time (over 3 h) and concentration (1–10 μmol/l) dependent. 2. To determine if these effects occurred in vivo, four volunteers received intravenous infusions on four occasions, to give constant plasma aspirin concentrations of 0, 1, 2 and 4 μmol/l over 3 h. Infusions were performed at intervals of at least 2 weeks. 3. Before and during the infusions, blood was taken for assay of aspirin concentrations, and measurements of platelet aggregation in response to collagen, adenosine 5′-pyrophosphate and arachidonate. Thromboxane generation after stimulated platelet aggregation and whole-blood coagulation was also measured. 4. At each aspirin concentration, both platelet aggregation and thromboxane generation in response to collagen and arachidonate were inhibited progressively over the 3 h infusion period. Greatest inhibition was seen during the 4 μmol/l infusion, which produced maximal or near-maximal inhibition by the third hour. 5. Thromboxane generated during whole-blood coagulation was similarly inhibited in both a time- and concentration-dependent manner throughout all aspirin infusions. 6. The progressive nature of the inhibition of platelet function with these low aspirin concentrations may be due to either slow aspirin transport across the platelet membrane or delayed interaction with cyclo-oxygenase.

A Comparison of the Effect of Decorsin and Two Disintegrins, Albolabrin and Eristostatin, on Platelet Function

1995 ◽  
Vol 74 (05) ◽  
pp. 1316-1322 ◽  
Author(s):  
Mary Ann McLane ◽  
Jagadeesh Gabbeta ◽  
A Koneti Rao ◽  
Lucia Beviglia ◽  
Robert A Lazarus ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Sequence Similarity ◽  
Platelet Aggregation Inhibitors ◽  
Antiplatelet Drug ◽  
Rgd Sequence ◽  
Fibrinogen Receptor ◽  
Activated Platelets

SummaryNaturally-occurring fibrinogen receptor antagonists and platelet aggregation inhibitors that are found in snake venom (disintegrins) and leeches share many common features, including an RGD sequence, high cysteine content, and low molecular weight. There are, however, significant selectivity and potency differences. We compared the effect of three proteins on platelet function: albolabrin, a 7.5 kDa disintegrin, eristostatin, a 5.4 kDa disintegrin in which part of the disintegrin domain is deleted, and decorsin, a 4.5 kDa non-disintegrin derived from the leech Macrobdella decora, which has very little sequence similarity with either disintegrin. Decorsin was about two times less potent than albolabrin and six times less potent than eristostatin in inhibiting ADP- induced human platelet aggregation. It had a different pattern of interaction with glycoprotein IIb/IIIa as compared to the two disintegrins. Decorsin bound with a low affinity to resting platelets (409 nM) and to ADP-activated platelets (270 nM), and with high affinity to thrombin- activated platelets (74 nM). At concentrations up to 685 nM, it did not cause expression of a ligand-induced binding site epitope on the (β3 subunit of the GPIIb/IIIa complex. It did not significantly inhibit isolated GPIIb/IIIa binding to immobilized von Willebrand Factor. At low doses (1.5-3.0 μg/mouse), decorsin protected mice against death from pulmonary thromboembolism, showing an effect similar to eristostatin. This suggested that decorsin is a much more potent inhibitor of platelet aggregation in vivo than in vitro, and it may have potential as an antiplatelet drug.

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.

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