knockdown of Orai1 reduced CCE in STIM1-overexpressing mouse PASMCs. A and B: STIM1, Orai1, and GAPDH proteins were detected in cells infected with adenovirus containing green fluorescent protein (Ad-GFP) transfected with 200 nM scrambled siRNA. The expression of STIM1 but not Orai1 or GAPDH increased markedly in cells infected with STIM1-GFP-adenovirus (Ad-GFP-STIM1) transfected with scrambled siRNA. The expression of Orai1 but not STIM1 or GAPDH was reduced significantly in STIM1-overexpressing cells transfected with 200 nM Orai1 siRNA. Experiments were performed in 3 separate Western blot analyses (**P < 0.01, ANOVA). C: overexpression of STIM1 in scrambled siRNA-transfected cells caused an increase in CPA-induced transient and sustained rise in fura-2 fluorescence ratio in the presence of 10 μM nifedipine. The increases in fluorescence ratio were reduced in Orai1 siRNA-transfected cells overexpressed with STIM1. D: bar graph showing mean changes in transient and sustained increase in [Ca2+]i caused by 10 μM CPA after readdition of 2 mM Ca2+ in the presence of 10 μM nifedipine, in GFP-infected cells transfected with scrambled siRNA (filled bars, n = 33), in STIM1-overexpressing cells transfected with scrambled siRNA (shaded bars, n = 65), and in STIM1-overexpressing cells transfected with Orai1 siRNA (open bars, n = 50). *P < 0.05, compared with GFP-infected cells transfected with scrambled siRNA and STIM1-overexpressing cells transfected with Orai1 siRNA (ANOVA). E: overexpression of STIM1 in scrambled siRNA-transfected cells caused a CPA-induced increase in Mn2+ quench of fura-2 fluorescence in the presence of 10 μM nifedipine. The increases in Mn2+ quench of fura-2 fluorescence was reduced in Orai1 siRNA-transfected cells overexpressed with STIM1. F: bar graph showing percentage change in fura-2 quench rate after store-depletion in the presence of 10 μM nifedipine, in GFP-infected cells transfected with scrambled siRNA (filled bars, n = 40), in STIM1-overexpressing cells transfected with scrambled siRNA (shaded bars, n = 95), and in STIM1-overexpressing cells transfected with Orai1 siRNA (open bars, n = 57). **P < 0.01, compared with GFP-infected cells transfected with scrambled siRNA and STIM1-overexpressing cells transfected with Orai1 siRNA (ANOVA).