Key result
Platelets in the midportion of the centrifuged tube were most extensively aggregated by ADP, while those in the lowest portion aggregated least, suggesting preactivation and deactivation.
Platelets obtained via centrifugation with an erythrocyte agglutinating agent exhibit varying aggregation capabilities depending on their location in the tube, suggesting preactivation and deactivation states.
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May affect platelet aggregation assay interpretation; leaves open clinical relevance pending human validation.
Human blood anticoagulated with a serine protease inhibitor was centrifuged with an erythrocyte agglutinating agent in the bottom of the tube. Platelet rich plasma (PRP) obtained in this manner contained platelets with different ability to aggregate with ADP located in the various layers of the tube. Platelets in the midportion of the tube were most extensively aggregated by a standard dose of ADP (1.6 micro M) and mechanical stirring. Platelets in the lowest portion aggregated least, but still showed normal "shape change" when they were stimulated. The uppermost platelets in the tube also showed somewhat reduced aggregation compared with the midportion. These observations could not be explained by differences in platelet concentrations. On a descriptive basis the platelets in the midportion of the tube are designated preactivated and the lowermost platelets deactivated.
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Ivar Aursnes (1982) studied this question. Centrifugation with an erythrocyte agglutinating agent and ADP stimulation vs. Comparison between different layers of the tube was evaluated on Platelet aggregation ability. Platelets in the midportion of the centrifuged tube were most extensively aggregated by ADP, while those in the lowest portion aggregated least, suggesting preactivation and deactivation.
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