Platelets from GSK3β^+/− mice are hypersensitive to agonist-stimulated aggregation, secretion of dense granule contents, and fibrinogen binding. (A) PRP from WT and GSK3β^+/− mice (2 × 10⁸/mL) were stimulated with mouse TRAP AYPGKF (0.6 mM) in the presence of luciferase (100 nM). Aggregation and ATP release were recorded with an optical aggregometer. A representative aggregation trace is shown. (B) The maximal percent aggregation in response to varying concentrations of AYPGKF was measured. The mean (± SD) for 4 experiments is shown for WT platelets (○) and GSK3β^+/− platelets (●). ** indicates the difference between WT and GSK3β^+/− is statistically significant (P < .01, n = 4, unpaired Student t test). (C) The amount of ATP secretion (nmol/5 × 10⁷ platelets) in response to 0.6 mM mouse TRAP was measured in 6 experiments: the mean (± SD) is shown; ** indicates the difference between WT and GSK3β^+/− is statistically significant (P < .01, unpaired Student t test; WT, □; GSK3β^+/− ■). (D) The percent of cells binding fibrinogen following stimulation with varying concentrations of mouse TRAP AYPGKF is shown: ○ for WT cells, ● for GSK3β^+/− platelets (mean ± SD; ** indicates statistical significance, P < .01, unpaired Student t test for 3 experiments).