Fig. 2.

Orai1 mediates capacitative Ca²⁺ entry (CCE) in mouse PASMCs. A and B: Orai1 protein and GAPDH were detected in nontransfected mouse PASMCs and in PASMCs transfected with 200 nM scrambled small interfering RNA (siRNA; negative control). The expression of Orai1 but not GAPDH was reduced significantly in cells transfected with 200 nM Orai1 siRNA. Experiments were performed in 3 separate Western blot analyses (**P < 0.01, ANOVA). C: siRNA knockdown of Orai1 reduced the cyclopiazonic acid (CPA)-induced transient but not the sustained increase in fura-2 fluorescence ratio in the presence of 10 μM nifedipine. 0Ca, Ca²⁺-free solution. D: bar graph showing mean changes in transient and sustained increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i) caused by 10 μM CPA after readdition of 2 mM Ca²⁺ in the presence of 10 μM nifedipine, in negative control cells (filled bars, n = 89), and in Orai1 siRNA-transfected cells (open bars, n = 86). **P < 0.01 (unpaired t-test). E: siRNA knockdown of Orai1 reduced the increase in Mn²⁺ quench of fura-2 fluorescence caused by 10 μM CPA in the presence of 10 μM nifedipine. AU, arbitrary units. F: bar graph showing percentage change in fura-2 quench rate after store-depletion in the presence of 10 μM nifedipine, in negative control cells (filled bar, n = 79), and in Orai1 siRNA-transfected cells (open bar, n = 86). **P < 0.01 (unpaired t-test).