Figure 7.

Store depletion activates Ca²⁺-activated Cl⁻ currents in rabbit pulmonary artery smooth muscle cells. A, Three families of membrane currents recorded from the same smooth muscle cell and elicited by the voltage-clamp protocol displayed below the traces. The traces in a were recorded in the presence of 1 μM nifedipine (Nif). In the continued presence of Nif, the cell was then superfused with 30 μM cyclopiazonic acid (CPA) for 5 minutes (b) to deplete the stores. Subpanel c shows a family of traces recorded after application with the nonselective cation channel inhibitor SKF-96365 (SKF; 50 μM), with CPA and Nif still present. B, Mean current-voltage relationships for current density (pA/pF), measured at the end of the second step to +90 mV, as a function of the voltage during the preceding step. Each data point represents the mean ± SEM current recorded in the presence of 1 μM Nif alone (open circles; n = 5), with 30 μM CPA and Nif (filled circles; n = 12), or with Nif, CPA, and 50 μM SKF (filled squares; n = 4). There were no significant differences between the Nif-alone and Nif + CPA + SKF groups. All data points in the Nif + CPA group were significantly different from those of the other two groups (with a maximum P value of <0.05). The 3 lines passing through the data points represent linear regression fits. Reproduced from Angermann et al.¹³⁸ with permission from the National Research Council of Canada.