The Mechanism of Cold-Induced Platelet Hyperfunction.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1651-1651
Author(s):  
Qiang Han ◽  
Junmei Chen ◽  
Yuandong Peng ◽  
Angela L. Bergeron ◽  
Li Liu ◽  
...  
Keyword(s):  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Cold Treatment ◽  
Flow Chamber ◽  
Type Iii Collagen ◽  
Clotting Time ◽  
Functional Studies ◽  
Lower Shear ◽  
Induced Aggregation

Abstract Refrigerated platelets function better when transfused than do platelets stored at room temperature, although chilled and rewarmed platelets do not survive long in the circulation. Here, we describe the one possible mechanism of this increase in the hemostatic function of platelets upon cold treatment. Cold exposure has been demonstrated to cluster GP Ib-IX complexes on platelets, enabling platelet recognition and phagocytosis by macrophages. We find that, in addition to increasing the binding to the leukocyte integrin Mac-1 (aMb2), clustering of GP Ib-IX complexes also augments von Willebrand factor (VWF)-related functions. Before the functional studies, platelets were chilled to 4°C for 2 hr and rewarmed to 37°C for 30 min. Chilled, rewarmed platelets, whether in platelet-rich plasma (PRP), whole blood, or reconstituted whole blood (all anticoagulated with Cirtate Sodium) perfused through a parallel-plate flow chamber (36 dynes/cm2) attached in greater numbers to VWF-coated surfaces than did platelets from the same donor kept at 37°C or 22°C. The increased function was also reflected in increased thrombus number and size on a surface of type III collagen. The surface coverage, an indicator of thrombus formation, increased from 10% to 25% upon cold. Chilled, rewarmed platelets also responded to lower doses of a VWF-specific agonist, ristocetin Chilled, rewarmed platelets showed 80% aggregation while control platelet only had 10% aggregation at low concentration of ristocetin (0.5mg/ml) treatment, and displayed a decreased threshold for shear-induced aggregation, aggregating at lower shear rates than control platelets at both 22°C and 37°C. Finally, when tested in a platelet function analyzer (PFA-100), chilled, rewarmed platelets demonstrated significantly shorter closure times than control platelets using both epinephrine/collagen and ADP/collagen cartridges. The epinephrine/collagen cartridges clotting time of chilled platelets decreased from normal 180 s to 162 s and ADP/collagen cartridges clotting time decreased from 118s to 99s. To exclude that the observed functional increases were not due to changes in GP Iba expression or prior platelet activation, we evaluated by flow cytometry the surface levels of GP Iba, P-selectin, and activated αIIbβ3.(antibody PAC-1 binding). We found no differences in any of these parameters between chilled, rewarmed platelets and control platelets. These results suggest that, if their rapid clearance can be prevented, cold-stored platelets may have enhanced hemostatic function of potential benefit in the bleeding patient. The results also caution, however, that trials will be necessary to exclude potential thrombotic consequences of infusing hyperfunctional, refrigerated platelets.

Combined Dabigatran and Antiplatelet Agents Assessed by the Novel Microchip-Based Flow Chamber System

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1167-1167
Author(s):  
Kenichi Tanaka ◽  
Kazuya Hosokawa ◽  
Tomoko Ohnishi ◽  
Hisayo Sameshima ◽  
Takehiko Koide ◽  
...  
Keyword(s):  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Antiplatelet Agents ◽  
Lag Time ◽  
Flow Chamber ◽  
Chamber System ◽  
Shear Rates ◽  
Antithrombotic Effects ◽  
Flow Pressure

Abstract Abstract 1167 Evaluation of the overall antithrombotic activity of dabigatran in combination with antiplatelet agents is difficult because plasma-based clotting for dabigatran, and platelet aggregometry in anticoagulated blood are two separate tests which do not reflect physiological interactions between soluble factors and platelets. The use of a flow chamber could be more suitable in evaluating a flow-dependent platelet activation and coagulation responses. The aim of the current study was to comparatively evaluate antithrombotic effects of dabigatran in combination with dual antiplatelet therapy (aspirin plus P2Y12 blockade) using the microchip-based flow chamber (T-TAS, Fujimori Kogyo, Japan)(1), and thrombin generation (TG) assay (Thrombinoscope, Maastricht, the Netherlands)(2). After the local ethics committee approval, blood samples were obtained from consented 5 healthy volunteers in the tubes containing 3.2% sodium citrate. Whole blood samples were mixed with dabigatran (250, 500, 1000 nM), aspirin (100 nM) plus ARC-66096 (P2Y12 inhibitor, 1000 nM) at 25¡C for 10 min. Corn trypsin inhibitor (50 μg/ml) was used to prevent contact activation. The whole blood sample was perfused in the capillary pre-coated with collagen and thromboplastin at the shear rate of 240 or 600 s−1. The process of thrombus formation was monitored by flow pressure increases inside the capillary; (i) lag time before it reaches 10 kPa (T10), (ii) occlusion time (OT) is the lag time before it reaches 80 kPa as thrombus completely occludes the capillary, and (iii) AUC30 is an area under the flow pressure curve (under 80 kPa) after 30 min of perfusion. For TG assay, platelet-rich plasma (platelet count 150 × 103/μl) was prepared from citrated whole blood. TG was triggered by adding 20 μl of CaCl2-fluorogenic substrate buffer to 80 μl of the sample mixed with tissue factor (1 pM) in each well. The lag time (min), and peak thrombin concentration (nM) were evaluated. In the flow chamber, dabigatran inhibited white thrombus formation in a concentration dependent manner at shear rates of 240 and 600 s−1(Fig. 1). At 500 nM of dabigatran, OT was prolonged by ∼2-fold from the (non-treated) control at both shear rates. The combination of aspirin and AR-C66096 only weakly suppressed thrombus formation, but it enhanced the antithrombotic efficacy of dabigatran at both shear rates (Fig. 1). In TG measurements using platelet-rich plasma, dabigatran at 500 nM prolonged the by 3.17-fold, and reduced the peak by 57.6% compared to the untreated control (Table 1). Aspirin and AR-C66096 weakly prolonged the lag time without affecting the peak height. There were relatively small changes in these parameters when antiplatelet agents were combined with dabigatran (Table 1). Our results suggest that combined antithrombotic effects of dabigatran, aspirin, and P2Y12inhibition can be demonstrated in the whole blood using the flow chamber system compared without additional plasma preparation required for TG assay. The re-calcified whole blood was perfused at the shear rate of 240 s−1 or 600 s−1. Asp/AR-C=aspirin and AR-C66096 Table 1. Lag time (min) Peak (nM) Native Asp/AR-C Native Asp/AR-C Control 6.8 ± 0.8 9.4 ± 3.2 92.1 ± 23.7 91.2 ± 29.5 Dabi 250 nM 18.6 ± 5.4 21.1 ± 4.5 69.3 ± 20.6 52.2 ± 13.6 Dabi 500 nM 21.6 ± 5.3 26.2 ± 10.2 53.0 ± 5.8 47.8 ± 9.1 Dabi 1000 nM 30.2 ± 5.6 35.1 ± 6.3 23.0 ± 6.9 22.0 ± 8.4 Dabi=dabigatran, Native=no antiplatelet agents, Asp/AR-C=aspirin and AR-C66096 Disclosures: Hosokawa: Fujimori Kogyo: Employment. Ohnishi:Fujimori Kogyo: Employment. Sameshima:Fujimori Kogyo: Employment.

Lack of Stability of Aggregates after Thrombin-Induced Reaggregation of Thrombin-Degranulated Platelets

1992 ◽  
Vol 67 (04) ◽  
pp. 453-457 ◽  
Author(s):  
Raelene L Kinlough-Rathbone ◽  
Marian A Packham ◽  
Dennis W Perry ◽  
J Fraser Mustard ◽  
Marco Cattaneo
Keyword(s):  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Aggregate Stability ◽  
Relative Importance ◽  
Platelet Aggregates ◽  
The Stability ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

SummaryThe stability of platelet aggregates is influenced by the extent of the release of granule contents; if release is extensive and aggregation is prolonged, deaggregation is difficult to achieve. The relative importance of the contributions of released substances to aggregate stability are not known, although stable thrombin-induced aggregates form in platelet-rich plasma from patients with barely detectable plasma or platelet fibrinogen, and ADP stabilizes thrombin-induced aggregates of platelets from patients with delta storage pool deficiency which otherwise deaggregate more readily than normal platelets. We degranulated platelets with thrombin (0.9 U/ml caused greater than 90% loss of delta and alpha granule contents) and recovered them as individual platelets in fresh medium. The degranulated platelets were reaggregated by thrombin (2 U/ml). To prevent continuing effects of thrombin, FPRCH2C1 was added when thrombin-induced aggregation of thrombin-degranulated platelets reached its maximum. EDTA (5 mM) or EGTA (5 mM) added at maximum aggregation did not deaggregate these platelets, indicating that the stability of these aggregates does not depend on Ca2+ in the medium. Whereas with control platelets a combination of PGE1 (10 μM) and chymotrypsin(10 U/ml) was required for deaggregation, with thrombin-degranulated platelets either PGE1 or chymo-trypsin alone caused extensive deaggregation. The rate and extent of deaggregation of thrombin-degranulated platelets by a combination of PGE1 and chymotrypsin was greater than with control platelets.Electron microscope gold immunocytochemistry using antihuman fibrinogen IgG, anti-von Willebrand factor and anti-fibronectin showed a) that fibrinogen in the vacuoles of degranulated platelets was visible at focal points of platelet contact in the aggregates, but that large areas of platelet contact had no fibrinogen detectable between them; and b) in comparison to fibrinogen, little fibronectin or von Willebrand factor (vWf) was detectable in the platelets.Since the linkages between thrombin-degranulated platelets reaggregated by thrombin can be disrupted either by raising cAMP (thus making glycoprotein IIb/IIIa unavailable) or by proteolysis, these linkages are less stable than those formed between normal platelets. It might therefore be expected that platelets that take part in thrombus formation and then recirculate are likely to form less stable thrombi than platelets that have not released their granule contents.

Dipyridamole Inhibits Platelet Aggregation in Whole Blood

1983 ◽  
Vol 50 (04) ◽  
pp. 852-856 ◽  
Author(s):  
P Gresele ◽  
C Zoja ◽  
H Deckmyn ◽  
J Arnout ◽  
J Vermylen ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Significant Negative Correlation ◽  
Significant Inhibition ◽  
Oral Drug ◽  
Human Blood Samples ◽  
Induced Aggregation

SummaryDipyridamole possesses antithrombotic properties in the animal and in man but it does not inhibit platelet aggregation in plasma. We evaluated the effect of dipyridamole ex vivo and in vitro on platelet aggregation induced by collagen and adenosine- 5’-diphosphate (ADP) in human whole blood with an impedance aggregometer. Two hundred mg dipyridamole induced a significant inhibition of both ADP- and collagen-induced aggregation in human blood samples taken 2 hr after oral drug intake. Administration of the drug for four days, 400 mg/day, further increased the antiplatelet effect. A significant negative correlation was found between collagen-induced platelet aggregation in whole blood and dipyridamole levels in plasma (p <0.001). A statistically significant inhibition of both collagen (p <0.0025) and ADP-induced (p <0.005) platelet aggregation was also obtained by incubating whole blood in vitro for 2 min at 37° C with dipyridamole (3.9 μM). No such effects were seen in platelet-rich plasma, even after enrichment with leukocytes. Low-dose adenosine enhanced in vitro inhibition in whole blood.Our results demonstrate that dipyridamole impedes platelet aggregation in whole blood by an interaction with red blood cells, probably involving adenosine.

Enhanced platelet aggregation and activation under conditions of hypothermia

2007 ◽  
Vol 98 (12) ◽  
pp. 1266-1275 ◽  
Author(s):  
Ruben Xavier ◽  
Ann White ◽  
Susan Fox ◽  
Robert Wilcox ◽  
Stan Heptinstall
Keyword(s):  
Cardiac Surgery ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Baseline Levels ◽  
Spontaneous Aggregation ◽  
High Concentrations ◽  
Induced Aggregation ◽  
P2y12 Antagonist

SummaryThe effects on platelet function of temperatures attained during hypothermia used in cardiac surgery are controversial. Here we have performed studies on platelet aggregation in whole blood and platelet-rich plasma after stimulation with a range of concentrations of ADP, TRAP, U46619 and PAF at both 28°C and 37°C. Spontaneous aggregation was also measured after addition of saline alone. In citrated blood, spontaneous aggregation was markedly enhanced at 28°C compared with 37°C. Aggregation induced by ADP was also enhanced. Similar results were obtained in hirudinised blood. There was no spontaneous aggregation in PRP but ADP-induced aggregation was enhanced at 28°C. The P2Y12 antagonist AR-C69931 inhibited all spontaneous aggregation at 28°C and reduced all ADP-induced aggregation responses to small, reversible responses. Aspirin had no effect. Aggregation was also enhanced at 28°C compared with 37°C with low but not high concentrations of TRAP and U46619. PAF-induced aggregation was maximal at all concentrations when measured at 28°C, but reversal of aggregation was seen at 37°C. Baseline levels of platelet CD62P and CD63 were significantly enhanced at 28°C compared with 37°C. Expression was significantly increased at 28°C after stimulation with ADP, PAF and TRAP but not after stimulation with U46619. Overall, our results demonstrate an enhancement of platelet function at 28°C compared with 37°C, particularly in the presence of ADP.

Blockade of adenosine diphosphate receptors P2Y12 and P2Y1 is required to inhibit platelet aggregation in whole blood under flow

Blood ◽  
2001 ◽  
Vol 98 (12) ◽  
pp. 3340-3345 ◽  
Author(s):  
Nancy A. Turner ◽  
Joel L. Moake ◽  
Larry V. McIntire
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Thrombus Formation ◽  
Direct Shear ◽  
Flow Conditions ◽  
Initial Adhesion ◽  
Platelet Deposition ◽  
Adp Receptors ◽  
Induced Aggregation ◽  
Control Samples

Abstract Using heparinized whole blood and flow conditions, it was shown that adenosine 5′-diphosphate (ADP) receptors P2Y12 and P2Y1 are both important in direct shear-induced platelet aggregation and platelet aggregation subsequent to initial adhesion onto von Willebrand factor (vWf)–collagen. In the viscometer, whole blood was subjected to shear rates of 750, 1500, and 3000 s−1 for 30 seconds at room temperature. The extent of aggregation was determined by flow cytometry. The P2Y12antagonist AR-C69 931MX (ARMX) reduced shear-induced aggregation at these rates by 56%, 54%, and 16%, respectively, compared to control samples. Adenosine 3′,5′-diphosphate (A3P5P; P2Y1antagonist) inhibited shear-induced aggregation by 40%, 30% and 29%, respectively, compared to control samples. Blockade of both ADP receptors at 3000 s−1 with ARMX plus A3P5P further reduced the platelet aggregation by 41% compared to the addition of ARMX alone (57% compared to control samples). Using a parallel-plate flow chamber, whole blood was perfused over bovine collagen type 1 at a wall shear rate of 3000 s−1 for 60 seconds. Platelet deposition was quantified with epifluorescence video microscopy and digital image processing. Blockade of P2Y12 alone or blockade of P2Y1 alone did not reduce thrombus formation on vWf–collagen. In contrast, blockade of both P2Y12 and P2Y1 reduced platelet deposition by 72%. These results indicate that combinations of antagonists of the ADP receptors P2Y12 and P2Y1 are effective inhibitors of direct shear-induced platelet aggregation and of platelet aggregation subsequent to initial adhesion under flow conditions. Inhibitors of these pathways are potentially useful as antiarterial thrombotic agents.

CONGENITAL MACROTHROMBOCYTOPENIA, LEUCOCYTE INCLUSIONS, DEAFNESS AND PROTEINURIA: FUNCTIONAL AND ELECTR0NMICROSCOPIC OBSERVATIONS ON PLATELETS AND MEGAKARYOCYTES

1987 ◽  
Author(s):  
D Blockmans ◽  
M J Heynen ◽  
J Vermylen ◽  
R Verwilghen
Keyword(s):  
Whole Blood ◽  
Plasma Membranes ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Central Zone ◽  
Peripheral Zone ◽  
Impedance Method ◽  
Functional Studies ◽  
Ultrastructural Studies ◽  
Granulocyte Function

We report here a female patient of 33 years with a variant of Alport's syndrome (macrothrombocytopenia, leucocyte inclusions, deafness and proteinuria). The bleeding problems consisted of ecchymoses and menorrhagia, the deafness was of the ^ensorineural type. The platelet count in whole blood was 14.109/I, the mean platelet volume 22.8 μm3 . The template bleeding time exceeded 30 minutes. Ultrastructural studies of the peripheral blood revealed giant spheroid platelets with a high density of organelles, an abundance of vacuoles and an apparently disorganized microtubular system. In addition, unusual granule free areas were observed in the neutrophils of the patient and her mother. Granulocyte function was normal, except for a low myeloperoxidase content.Functional studies of the platelets in platelet rich plasma showed normal aggregation curves related to the low platelet number, although no shape change could be elicited. Platelet aggregation studies in whole blood (impedance method) gave supernormal aggregation curves; this suggests the limited usefulness of this technique in patients with such large platelets.The bone marrow contained numerous dysplastic megakaryocytes. In the mature granular megakaryocytes vacuoles and cysternae were organized in a radiating pattern demarkating elongated platelet territories. The platelet producing megakaryocytes showed fragmentation of the central zone and discharge of platelets through openings of the peripheral zone. These megakaryocytes had an immunological phenotype resembling that of very young cells (TR 14%, GP IIa 17% and GP IIIa 7%). The conversion of the elongated platelet territories into giant spheroid platelets probably results from remodelling within the circulation. The internalisation of plasma membranes would give rise to the extended invaginated canalicular system. Further studies are needed to explain the exact pathogenesis of this syndrome.

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.

Monitoring of coagulation factor therapy in patients with von Willebrand disease type 3 using a microchip flow chamber system

2017 ◽  
Vol 117 (01) ◽  
pp. 75-85 ◽  
Author(s):  
Margareta Holmström ◽  
David E. Schmidt ◽  
Kazuya Hosokawa ◽  
Margareta Blombäck ◽  
Paul Hjemdahl ◽  
...  
Keyword(s):  
Whole Blood ◽  
Thrombus Formation ◽  
Flow Chamber ◽  
Von Willebrand Disease ◽  
High Shear ◽  
Fviii Activity ◽  
Concentrate Treatment ◽  
Type 3 ◽  
Von Willebrand ◽  
Low Shear

SummaryPatients with type 3 von Willebrand disease (VWD-3) have no measurable levels of VW factor (VWF) and usually require treatment with VWF-FVIII concentrate to prevent and/or stop bleeding. Even though the patients are treated prophylactically, they may experience bleeding symptoms. The aim of this study was to evaluate the effect of VWF-FVIII concentrate treatment in VWD-3 patients with the Total Thrombus Analysis System (T-TAS®), which measures thrombus formation under flow conditions. Coagulation profiles of 10 VWD-3 patients were analysed using T-TAS before and 30 minutes after VWF-FVIII concentrate (Haemate®) injection. Results were compared to VWF- and FVIII activity in plasma, and results with thromboelastometry and ris-tocetin-activated platelet impedance aggregometry (Multiplate®) in whole blood. For comparison, 10 healthy controls were also analysed with T-TAS. A median dose of 27 (range 15–35) IU/kg of VWF-FVIII concentrate increased VWF- and FVIII activity as expected. T-TAS thrombus formation was enhanced when a tissue factor/collagen-coated flow chamber was used at low shear, but treatment effects at high shear using a collagen-coated flow chamber were minimal. Whole blood coagulation assessed by thromboelastometry was normal and did not change (p > 0.05) but ristocetin-induced platelet aggregation improved (p < 0.001). In conclusion, T-TAS detects effects of VWF-FVIII concentrate treatment on coagulation-dependent thrombus formation at low shear, but minor effects are observed on platelet-dependent thrombus formation at high shear. The poor prediction of bleeding by conventional laboratory monitoring in VWD-3 patients might be related to insufficient restoration of platelet-dependent thrombus formation.

Impaired Platelet Aggregation after Cardiopulmonary Bypass in Man: Enhancement of Collagen-Induced Aggregation in whole Blood and Plasma by Adrenaline Ex Vivo

1995 ◽  
Vol 88 (3) ◽  
pp. 269-275 ◽  
Author(s):  
Valentine C. Menys ◽  
Philip R. Belcher ◽  
Mark I. M. Noble ◽  
George E. Drossos ◽  
Ravi Pillai ◽  
...  
Keyword(s):  
Whole Blood ◽  
Light Transmission ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Plasma Adrenaline ◽  
Platelet Counts ◽  
Percentage Decrease ◽  
Adrenaline Infusion ◽  
Spontaneous Aggregation ◽  
Induced Aggregation

1. We tested the effect of intravenous adrenaline at 0.55–1.10 nmol min−1 kg−1 (for 3–8 min, at 7–10 min post bypass; n = 7) on both microaggregation in hirudinized whole blood, using platelet counting, and macroaggregation in platelet-rich plasma, using optical aggregometry. Control (n = 12) blood samples were taken before and at 10 and 20 min after bypass. 2. Post-bypass plasma adrenaline levels (nmol/l) increased slightly in controls (1.0 versus 0.7 at 10 min, medians; P = 0.05) and markedly with adrenaline infusion (36 versus 0.5 before infusion, P = 0.02). Microaggregation (percentage decrease in single platelets) in stirred blood, reflecting largely ADP-dependent ‘spontaneous’ aggregation, was not influenced by adrenaline infusion. In contrast, collagen (0.2 μg/ml)-induced microaggregation in blood was enhanced by adrenaline (92% versus 41%, P = 0.02), with no change in controls (60% versus 53%, P = 0.61). 3. In controls, collagen (0.6 μg/ml)-induced macroaggregation in platelet-rich plasma (extent of increase in light transmission, cm) was impaired at 10 min post bypass (5.3 versus 12.1 before bypass, P = 0.01), but was enhanced by adrenaline (7.0 versus 3.6 before infusion, P = 0.02). Platelet counts (×109/1) were decreased postbypass (155 versus 220, P = 0.02) and were not influenced by adrenaline infusion (167, P = 0.93). 4. In conclusion, following bypass and at normocalcaemia, adrenaline enhances collagen-induced aggregation in both plasma and whole blood ex vivo, independently of any change in platelet counts, but has no effect on stirring-induced ‘spontaneous’ aggregation in blood.

GUARANA (Paullinia cupana) INHIBITS AGGREGATION IN WHOLE BLOOD

1987 ◽  
Author(s):  
D A F Chamone ◽  
M Ivany-Silva ◽  
C Cassaro ◽  
G Bellotti ◽  
C Massumoto ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Oral Intake ◽  
Inhibitory Effect ◽  
Impedance Method ◽  
Paullinia Cupana ◽  
Induced Aggregation

Guarana, a methylxanthine obtained from the seeds of Paullinia cupana has been largely used in the Amazon region by native indians during centuries as stimulant. We evaluated the effect of guarana on ex-vivo and in vitro platelet aggregation induced by adenosine-5-diphosphate (ADP) in human and rat whole blood with an impedance (Chrono-Log, model 500) and in their platelet rich plasma (PRP) with an optical aggregometer (Chrono-Log, model 440). Ex-vivo studies were carried out after single oral intake of guarana. Seven healthy volunteers (5 male and 2 female) aged 19-26 years who had taken no drugs for 10 days before, ingested 8gm of crude powder of guarana. Blood samples were drawn before and 1 hour after guarana intake. We observed a significative inhibition of platelet aggregation in whole blood meanwhile PRP was un changed as compared to basal values. In vitro studies were performed in whole blood and PRP from human volunteers and male Wis-tar rats. The combined effect of guarana and adenosine was also studied. A control aggregation was always run with saline. The results demonstrated an inhibition statistically significative (p < 0.001) of platelet aggregation in whole blood. Differently from whole blood the PRP with the same concentration of guarana did not result in inhibition of ADP induced aggregation when eva luated with the impedance method. The blood incubation with adenosine and guarana resulted in synergistic inhibitory effect that was much more strinking in whole blood than in PRP. Guarana fails to inhibit aggregation of rat platelets.Our results demonstrate that guarana prevents platelet aggregation in whole blood which depends on red blood cells, probably involving adenosine.

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