Comparative Analysis of Spontaneous and Stimulus-Evoked Calcium Transients in Proliferating and Differentiating Human Midbrain-Derived Stem Cells

Figure 6

Effect of thapsigargin and calcium on proliferating stem cells incubated in a calcium-free medium. The cells were dye loaded and washed in a calcium-containing medium and then incubated in a calcium-free medium with 10 μM EGTA. Thapsigargin (2 μM, final concentration) was added after initiation of the incubation. After incubation for 300 sec, 2 mM calcium (final concentration) was added to the cells. The results from one of three independent experiments are shown (a). Abscissa: time of incubation (sec). Ordinate: intracellular calcium content. The fluorescence intensity was normalized to the level of the fluorescence intensity of untreated cells (100%). Mean values and SEM from 31 cells. All the cells responded to the addition of thapsigargin and calcium. Peak values from all three experiments, after addition of thapsigargin (open column) and calcium (closed column) can be seen (b). Mean values and SEM from 31–64 cells. Taken together, 149 cells were studied in three independent experiments, and 98% of the cells responded to the addition of both thapsigargin and calcium.

(a)

(b)