RAPID REACTIONS OF PLATELETS STUDIED BY A QUENCHED-FLOW APPROACH - AGGREGATION KINETICS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 100  (6) , 866-886
Abstract
Understanding the nature and regulation of very early events in the [human] platelet activation sequence is an important goal. A general approach based on quenched-flow principles was therefore developed. Platelet reactions are initiated by mixing inducing agent with whole blood, PRP [platelet-rich plasma] or washed platelets and pumping the mixture through narrow-bore tubing with quenching (stopping the reaction) at the outlet. Reaction times < 1 s are feasible. The quenched-flow system was combined with a continuous-flow modification of resistive-particle counters to follow aggregation kinetics of single particles. Aggregation at 37.degree. C is extremely rapid: after a lag period of .apprx. 1 s, between 20 and 50% of platelets then aggregate per second (10 .mu.M ADP). Although the kinetics are 2nd order, data can be expressed as the percent of single platelets aggregating per second and treated as pseudo-1st order. This enables derivation of apparent maximal velocities of aggregation and inducer activation constants, for characterizing platelet reactivity.