Fig. 2. Sample Ca²⁺ tracing showing the change in the F₃₄₀/F₃₈₀ excitation fluorescence emission ratio from a human CSM cell.

Treatments and duration are indicated by solid lines. Baseline Ca²⁺ values were established during the first minute in a physiological salt solution (red dashed line). Cell depolarization with an 80 mM K⁺ solution initiated Ca²⁺ influx via voltage-gated Ca²⁺ channels. The height of the Ca²⁺ influx peak (blue arrow) and the area under the curve (AUC, orange area) were calculated to quantify Ca²⁺ influx activity. SR Ca²⁺ store was released by activating ryanodine receptors with 5 mM caffeine (Caf) and was measured by the height of the caffeine-induced peak (purple arrow). The undershoot from baseline was used to measure SERCA activity (green caret)