Synergistic effect of U46619 and TRAP on platelet aggregation. Aggregation was measured in PRP by the turbidimetric method (17, 18) by using a model 400 Lumi-aggregometer (Chronolog, Havertown, PA). PRP was stimulated (at arrow) with 3 μM or 6 μM TRAP (traces a and b, respectively), 1 μM or 2 μM U46619 (traces c and d, respectively), or 1 μM U46619 plus 3 μM TRAP (trace e). The aggregation traces are representative of three separate experiments.