Fig. 4. EphrinA1 inhibits the activation of Rac1 but does not affect the activation of Cdc42. (A) Quiescent VSMCs were seeded on tissue culture dishes coated with laminin and either Fc or ephrinA1/Fc (A1). Cells were harvested at the indicated times and processed for pull-down experiments. Rac1 activity is determined by the amount of GST-PBD-bound Rac1 (Rac1-GTP) normalized to total Rac1 in whole cell lysates. (B) Densitometric analysis of (A). Results are the mean±s.d. of three independent experiments. (C) Quiescent VSMCs were seeded on tissue culture dishes coated with laminin and either Fc or ephrinA1/Fc (A1). Cells were harvested at the indicated times and processed for pull-down experiments. Cdc42 activity is determined by the amount of GST-PBD-bound Cdc42 (Cdc42-GTP) normalized to total Cdc42 in whole cell lysates.