Fig. 3. p38 MAPK activity is not induced by SMC spreading on fibronectin. Suspended SMC were incubated for 30 minutes with 25 µM SB203580 or vehicle and then plated out in dishes coated with fibronectin for 0, 30 minutes and 3 hours in the presence or absence of PDGF (10 ng/ml). SMC lysates (30 µg) were analyzed by immunoblotting using antibodies directed against p38 MAPK-P and Hsp27-P. Blots were reprobed with an anti--actin antibody to ensure equal loading. These results are representative of four independent experiments.