Figure 3

The effect of ISO on the Ca²⁺signaling of airway SMCs. (A) A fluorescence image of part of an airway obtained by two-photon microscopy under resting conditions. L, lumen; ECs, epithelial cells; SMC, smooth muscle cell. Dotted line indicates the interface between ECs and SMCs. Scale bar = 15 μm. The intracellular Ca²⁺ signaling represented by (B) a line-scan plot, constructed from the white line across the SMC as indicated in A, and the sequence of recorded images and (C) a small ROI in the same airway SMC as shown in B in response to the MCh (200 nM) and ISO (1 μM). (D) The correlation of the Ca²⁺ oscillation frequency (dotted line) and airway area (solid line) in a representative experiment with contraction induced by MCh (200 nM) and relaxation induced by ISO (10 μM). The Ca²⁺ oscillation frequency was determined by the time interval between 2 adjacent peaks. The frequency of the Ca²⁺ oscillations was inversely coupled to the contraction of the airway. (E) The mean concentration-dependent relaxation (solid line, ■) and the change in the frequency of the Ca²⁺ oscillations (dash line, ▼) induced by ISO in airways contracted with MCh (200 nM). The mean Ca²⁺ oscillation frequency after ISO exposure was expressed as a ratio to the Ca²⁺ oscillation frequency during MCh exposure. As the concentration of ISO increased, the Ca²⁺ oscillation frequency decreased. Each point represents 5 to 8 experiments (mean ± S.E.) in different airways from at least 3 mice for the contraction data and 5 – 6 experiments in different cells from at least 3 mice for the Ca²⁺ oscillation data. Data were fitted with a logistic function.