Platelet activation in response to thrombin. (A) Platelet aggregation. Washed wild-type (+/+) and GPV-deficient (−/−) platelets were stirred and exposed to 1 (top) or 30 nmol/L (bottom) thrombin at 0 seconds. Results are representative of 3 experiments. (B) Platelet secretion of ATP. Washed wild-type (+/+) and GPV-deficient (−/−) platelets were exposed to 1 or 30 nmol/L thrombin and the peak ATP secretion was measured by lumiaggregometry. Data represent the mean ± SD of 4 to 6 experiments.