Fig. 7. Repression of Rac1 synthesis amplifies the ephrinA1-mediated inhibition of VSMC spreading. (A) Western blot analysis of whole cell lysates of VSMCs transfected with calcium phosphate alone (Control), with an siRNA targeting Rac1 (Rac1) or with an siRNA targeting RhoA (RhoA). 48 hours post-transfection, cells were lysed in SDS-PAGE loading buffer and analyzed by immunoblotting with specific antibodies to RhoA, Rac1, Cdc42 and p42 MAP kinase. (B) Representative phase-contrast microscopy of quiescent VSMCs cultured for 4 hours on tissue culture dishes coated with laminin (0.25 µg/cm²) and 0.5 µg of either Fc (L+0.5Fc) or ephrinA1/Fc (L+0.5A1). VSMCs were transfected with calcium phosphate alone (Control), with 20 nM siRNA Rac1 (Rac1) or 20 nM siRNA RhoA (RhoA). Bar, 20 µm. (C) The morphology of control (Control), siRNA Rac1 (Rac1) or siRNA RhoA (RhoA)-treated cells from eight randomly chosen fields were scored (spread or retracted). Data represent the mean±s.d. of three independent experiments.