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

Figure 4

Calcium-induced increase of cytosolic Ca²⁺ in differentiating cells incubated in the absence or presence of Na⁺. After dye loading in the presence of Ca²⁺, cytosolic Ca²⁺ was monitored in cells incubated in a calcium-free medium with or without Na⁺ and then 2 mM Ca²⁺ was added (arrow) (a). The area under the curve (AUC) of the effect of Ca²⁺ addition is shown (b). The fraction of cells that respond to the addition of 2 mM Ca²⁺ with increased cytosolic Ca²⁺ is shown (c). The cells were incubated in the absence and presence of Na⁺ and then exposed to 2 mM Ca²⁺ ((c), columns A, B). Columns C and D show the fraction of cells with spontaneous Ca²⁺ increase in the absence and presence of Na⁺. AUC of the spontaneous Ca²⁺ increase is shown in columns C and D in Figure 4(d). GraphPad Prism4 was used to calculate AUC, expressed as fluorescence intensity (excitation ratio 360 nm/380 nm) per cell per 12 min (b) and 20 min (d), respectively. Mean value and SEM from 7 and 9 independent experiments (Figure 4(a)). Mean values and SEM from 296 cells and 270 cells incubated in the absence or presence of sodium, respectively (Figure 4(b)). Mean values and SEM from 7–14 experiments (Figure 4(c)) and 226 cells and 384 cells in Figure 4(d) (columns C and D, resp.). Column D in Figure 4(c) represents the data shown in Figure 2.

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