Platelet aggregation in whole blood

The entire procedure is performed in plastic (polystyrene) tubes and carried out at room temperature. Blood is drawn from healthy adult volunteers, who had not received medication for the last 2 weeks. 9 ml venous blood are anti-coagulated with 1 ml of sodium citrate and kept in a closed tube at room temperature for 30-60 min until the start of the test. 

For the aggregation studies, 10 pi test substance or vehicle (control) are added to 480 pi citrated blood. Samples in closed tubes are pre-incubated for 5 min in a 37 °C water shaker bath at 75 strokes/min. Ten pi 

The following samples for the determination of the platelet count are prepared in duplicate  

control aggregation = spontaneous aggregation (without aggregating agent) 480 xl blood + 20 p i vehicle. Blood samples with 20% spontaneous aggregation are not used to test for induced aggregation. 

maximal aggregation 480 p.1 blood + 10 p i vehicle +10 pil aggregating agent. Values represent the maximal induced aggregation rate of the blood sample. 

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Gresele P Zoja C, Deckmyn H, et al. Dipyridamole inhibits platelet aggregation in whole blood. Thromb Haemost 1983 50 852-856. 

Kirk, R.I., Deitch, J.A., Wu, J.M., and Lerea, K.M., Resveratrol decreases early signalhng events in washed platelets but has httle effect on platelet aggregation in whole blood. Blood Cells Mol. Dis., 26, 144, 2000. 

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Jarvis GE, Evans RJ. PAF and not TXA, is an important mediator of endotoxin induced platelet aggregation in equine heparinised whole Mood in vitro. Blood Coagulation and Fibrinolysis 1996 7 194-198... 

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Serotonin has been found to exert an intense vasoconstrictor effect on the pulmonary circulation 1 . Although the pulmonary vasoconstrictor effect of serotonin can be demonstrated easily by pharmacological methods, its physiological and pathophysiological roles have not been unequivocally demonstrated. In fact, the infusion of serotonin (1. 85 - 5. 5 mcg/kg/min) into the pulmonary artery of seven human subjects produced a definite rise in pulmonary artery pressure in only one instancel. Most of the serotonin found in whole blood is stored in platelets. This would imply that in the process of platelet aggregation to form a thrombus, serotonin would be available for release . Pulmonary vasoconstriction does occur as a result of pulmonary thrombosis. A further indication that serotonin could be implicated in the thrombosis-induced pulmonary vasoconstriction is the finding that 82 per cent of serotonin can be released from platelets by thrombin in five minutes. ... 

Many methods are available to measure platelet a egation in vitro. First, the blood sample is treated with an anticoagulant to avoid clotting of the blood in the test tube or in the aggregometer many different anticoagulants are used, which all differ in their mechanism of action. Second, platelet aggregation can be measured in whole blood, in platelet-rich plasma, or (to remove the influence of the... 

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