Fig. 4. EGF elicits a specific Ca2+ response. (A) A series of concentrations of EGF were evaluated, with images acquired every 789 milliseconds and data plotted as a percentage change in average fluorescence. The darker lines represent the response to EGF. The higher the concentration of EGF, the higher the number of cells recruited and the faster the response time. Cells incubated in 1 µM tyrphostin AG1478 for two hours before EGF addition did not respond. HEPES-buffered saline, lacking any growth factor (negative control) or containing 25 ng/ml PDGF or FGF-2, did not induce a detectable response. Images are representative of three independent experiments. (B) HCE-Ts migrated to EGF, with a maximal response seen at a concentration of 10 ng/ml EGF. In contrast, the same cells did not migrate to PDGF within the concentration range of 0.1 to 100 ng/ml PDGF. One representative experiment is shown in which the number of cells migrating per 10x field (average of 10 fields) was calculated (+/–, s.d.). Cells did not migrate in the absence of growth factor (negative control, (–)), but migrated extensively in the presence of 10% FBS (positive control, (+)).
