FIGURE 2.

Store-operated Ca²⁺ entry in fetal skeletal muscle cells. (A) High-K⁺ bath solution did not trigger intracellular Ca²⁺ release in an E16 cell preincubated in 0 Ca²⁺ for ∼2 h. Perfusion of 2 mM Ca²⁺ led to sustained elevation of cytosolic [Ca²⁺]_i. No further increase was observed when [Ca²⁺]_o was applied for the second time. Second exposure to high-K⁺ triggered transient elevation of [Ca²⁺]_i, indicative of SR Ca²⁺ refilling. (B) The cell was pretreated with thapsigargin (10 μM) for 10 min. Switching the bath solution from 0 Ca²⁺ to 2 mM Ca²⁺ led to elevation of [Ca²⁺]_i via SOCE, which was inhibited by 2-APB. (C) Quenching of Fura-2 fluorescence by 0.5 mM Mn²⁺ in a cell with passively depleted SR Ca²⁺ content. 5 μM nifedipine did not affect the rate of Fura-2 quenching. (D) Mn²⁺ quenching of Fura-2 measured in the same cell, in the control condition with passively depleted SR Ca²⁺ content, after addition of 10 μM thapsigargin, and after addition of 20 μM 2-APB. (E) Mn²⁺ entry rate was reversibly and reproducibly decreased when the bath solution was changed from control to a high-K⁺ solution.