Fig. 6.

Thapsigargin induced a transient rise in cytosolic sodium prior to endoplasmic reticulum calcium release. PAECs were treated with doxycycline as described in Fig. 2 legend and then loaded with ANG 2-AM or fura 2-AM to measure intracellular sodium or calcium, respectively. Thapsigargin was applied in the absence of extracellular calcium, and cytosolic sodium and calcium responses were evaluated. Raw data were synchronized according to the time at which thapsigargin was added and converted to a maximal response scale (0–100% of maximal response), and sodium and calcium release phases were compared. For studies conducted in the presence of Orai1, [Na⁺]_i data included 17 experiments in which 182 cells were analyzed and [Ca²⁺]_i data included 19 experiments; for studies conducted in the absence of Orai1, [Na⁺]_i data included 15 experiments in which 163 cells were analyzed and [Ca²⁺]_i data included 26 experiments. Data reveal that the sodium peak occurred prior to the calcium peak but was of shorter duration. Similar results were obtained in the presence (A) and absence (B) of Orai1. Mean value from these experiments is shown. Orai1 silencing did not change peak [Na⁺]_i or [Ca²⁺]_i signal (P = not significant).