Figure 3. Concentration-dependent effects of imatinib on PDGF-induced versus insulin-induced receptor phosphorylation. Serum-deprived (24 h) RGC-5 cells were pretreated without (control) or with increasing concentrations of imatinib (0.1 µM to 30 µM) for 30 min. Subsequently, control and imatinib-treated cells were stimulated with either 30 ng/ml PDGF or 30 nM insulin for 6 min. The cell lysates were subjected to immunoblot analysis for receptor tyrosine phosphorylation (A, B) using the indicated primary antibodies (See Methods). To normalize the changes in protein phosphorylation in the immunoblots, β-actin was used as an internal control. Note: For data analyses, PDGF- or insulin-induced receptor phosphorylation in the absence of imatinib was normalized to 100%. The respective linear graphs shown are the mean±SEM values from 3 experiments. The asterisk denotes a p<0.05 compared with the respective PDGF-induced receptor phosphorylation.