Inhibition of III1-C mediated ERK activation by various integrin inhibitors. RASMCs were collected in DMEM+0.5% BSA and were then either left in suspension in the absence (-) or presence of PDGF (PDGF), or plated onto dishes precoated with either fibronectin (FN), III1-C (C and C+... lanes), or III 11-C (11C), as described in the legend to Fig. 5. Some samples of cells plated onto III1-C also contained either 100 μg/ml heparin (C+Hep), 10 mM EDTA (C+EDTA), 50 μg/ml anti-β1 blocking mAb Ha2/5 (pi), 0.5 mg/ml GRGDSP peptide (RGD), 0.5 mg/ml GRADSP peptide (RAD), or combinations of heparin plus integrin inhibitors, as indicated. After 30 min at 37°C cells were lysed in SDS-PAGE sample buffer and samples were analyzed by immunoblotting with anti-phospho-p44/42 MAPK antibodies (Phos-ERK panels). Blots were then stripped and reprobed with anti-ERK antibodies (ERK panels) to analyze protein loading. The experiment was done 3 times with similar results each time.