Figure 5.

Plots showing the individual (gray curves) and average (black curve) calcium response of 50 representative cells when (A) HMVEC-d, (B)HeLa, and (C) U-251 cells were subject to rapid, single-pulse ionomycin stimulation of duration 100 ms. All three different types of cells, challenged by the 100-ms ionomycin stimulation, first exhibited rapidly-rising calcium transients with peak intensities that were lower than those under normal, single-pulse stimulation. After the first calcium transient was probed, the cells were also found to feature slowly-rising components as well as rapidly-rising components. These results suggest that the cells seemed to undergo a process where they, to maintain a certain calcium concentration, constantly released calcium from internal stores and received calcium from surrounding environments. Each plot is a representative result from at least three independent experiments where more than 200 cells in total were examined.