Platelet aggregation and secretion. (A) Platelet aggregations in citrated PRP from a control subject and 2 Q43P carriers (carriers 2 and 4) are shown with the indicated agonists and concentrations. Aggregations were performed in 5 unrelated carriers on separate occasions with similar results. (B) Platelet ATP secretion after stimulation of citrated PRP with ADP (5 μM, ▪) or collagen (2 μg/mL, ▦) shows a significantly decreased response in the 6 unrelated Q43P carriers compared with 6 healthy controls.