Interrelations of Platelet Aggregation and Secretion (original) (raw)

The mechanism of stimulus-response coupling in human platelets was investigated using a new instrument that simultaneously monitors aggregation and secretion. High concentrations of ADP triggered secretion only after aggregation was nearly complete, while lower concentrations or epinephrine prompted biphasic aggregation with secretion starting concurrently with the second phase. Secretion was found to be dependent on aggregation with indomethacin inhibiting this mechanism, denoted as aggregation-mediated platelet activation. Conversely, direct activation occurred independent of aggregation and was not inhibited by indomethacin. The study presents a model suggesting two activation mechanisms for platelets and emphasizes that secretion and second wave aggregation are parallel events.