PDGF-isoform dependent fibroblast proliferation assay. Fibroblasts were stimulated by PDGF-isoforms (-AA, -BB and -AB) at 2 ng/ml or 10 ng/ml for 72 hours after 1 hour pre-treatment with or without SU9518. SU9518 inhibited all three isoforms stimulated proliferation of fibroblasts (p < 0.05). The extent of inhibition was greater for PDGF-AB and -BB. Bars are means of 5 experiments ± SD.