Fig. 4.

Orai1 suppresses basal sodium leak in the presence of 2 mM extracellular calcium. PAECs were treated with doxycycline to silence Orai1, as described in Fig. 2 legend. Cells were loaded with the intracellular sodium dye ANG 2-AM, and the signal ratio (GFP/F₀) was repeatedly measured over time in the presence of 2 mM or low extracellular calcium. Reducing extracellular calcium (A) and silencing Orai1 (B) resulted in an increase in cytosolic sodium, characteristic of increased basal sodium leak. For studies conducted in the presence of both Orai1 and calcium, n = 6 experiments in which 67 cells were analyzed; for studies conducted in the presence of Orai1 and the absence of Ca²⁺, n = 8 experiments in which 88 cells were analyzed. For studies conducted in the absence of both Orai1 and Ca²⁺, n = 6 experiments in which 65 cells were analyzed; for studies conducted in the presence of Orai1 and the absence of Ca²⁺, n = 6 experiments in which 67 cells were analyzed. *P < 0.01.