FIGURE 4. Activation of adenylyl cyclase is required for the β2 agonist-induced store-operated calcium entry in alveolar epithelial cells.
(A) Measurement of calcium levels following albuterol administration in RLE cells pretreated with ICI-118,551 (1 µM, 30 min preincubation). (B) Measurement of calcium levels following albuterol administration in RLE cells pretreated with SQ-22536 (10 µM, 30 min preincubation). (C) Measurement of intracellular calcium levels in ATII cells treated with forskolin (50 µM). Perfusion was started in calcium-free media and switched to 2.5 mM calcium as indicated. (D) Peak [Ca2+]i and (E) rate of Ca2+ entry were measured in the cells after re-institution of 2.5 mM calcium to the media in cells incubated with forskolin (50 µM) or pre-incubated with ICI-118,551 (1 µM, 30 min preincubation) or SQ-22536 (10 µM, 30 min preincubation) previous addition of albuterol (5 µm). (F) Calcium concentration in RLE cells transfected with fluorescently labeled siRNA targeting STIM1 during treatment with forskolin (50 µM) along with Fura-2 and AlexaFluor5–46 fluorescence images. Results are for 3 experiments with 10–20 cells each. * p < 0.05, ** p < 0.01, *** p < 0.001.