Collagen-induced phosphorylation of AKT in human platelets. Washed platelets were pretreated with DMSO or LY294002 (50 μmol/L) as indicated for 15 minutes. Platelets were then treated with horse tendon type I collagen (50 μg/mL) or buffer (control) for 5 minutes. Whole-cell extracts (10⁷ cells/lane) were subjected to SDS-PAGE and Western blot analysis with an anti-phospho-AKT (A) or AKT antibody (B).