RNase protection assay analysis of IGF-IR (Panel A) and IGFBP-4 (Panel B) mRNA of SMC grown on fibronectin (FN) or AGE-modified FN (AGE-FN). Sub-confluent cells were pre-incubated in serum-free media for 24-h prior to a 24-h exposure to serum-free media (Control) or to 20 ng/mL PDGF-BB (PDGF-BB). Twenty micrograms of total RNA were cohybridized with hIGF-IR or hIGFBP-4 and 18S RNA riboprobes. A blot representative of three independent experiments is shown. O.D., optical density.