Actin assembly in response to thrombin. Following stimulation of washed murine platelets with 1 U/mL thrombin, platelets were fixed, permeabilized, and stained with fluorescent phalloidin. Flow cytometry was used to quantitate phalloidin binding in 100 000 cells, and analysis was performed using CELLQuest software. Shown is the mean ± SEM for 3 experiments. Platelet actin assembly in response to thrombin requires PLCβ2/β3 (A) but does not require PI3Kγ (B).