PGE₂ activates WT platelets. (A) Platelet spreading was increased by the addition of thrombin and 3 ng/mL of PGE₂. Treatment with 1.5 ng/mL of PGE₂ had no effect. (B) P-selectin expression, assessed by flow cytometry, was increased by thrombin and 3 ng/mL of PGE₂. Gray line denotes the expression of P-selectin in resting platelets; black lines denote the expression of P-selectin with (i) thrombin, (ii) 1.5 ng/mL of PGE₂, or (iii) 3 ng/mL of PGE₂ treatment. (C) β3 integrin phosphorylation was increased after treatment with thrombin or 3 ng/mL of PGE₂ but not 1.5 ng/mL of PGE₂. (D) Akt phosphorylation was increased after treatment with thrombin or 3 ng/mL of PGE₂ but not 1.5 ng/mL of PGE₂. *P < .05 or **P < .05 comparing treatment group with control.