Fig. 3. EGF initiates a delayed Ca²⁺ response in non-wounded cultures. Cells were loaded with fluo-3 AM, washed and background images collected. 25 ng/ml of EGF was added, and the response was monitored for one minute. A response was not detected until 30 seconds after EGF addition (arrows). The horizontal white bar in the top figure represents 50 µm. The intensity scale is also shown, with, red indicating the highest Ca²⁺ levels, and blue indicating the lowest Ca²⁺ levels. Images are representative of 10 independent experiments.