The expression of STIM1 and Orai1 in ARPE-19 cells. (A, B) Expression of Orai1 and STIM1 was determined by RT-PCR (A) and Western blots (B) in ARPE-19 cells. (C) F luorescent-based calcium assay was used to detect calcium signals. ARPE-19 cells were incubated in calcium free condition with 2 μM thapsigargin (TG). And then 2 mM calcium solution was added to detect the classical SOC entry.