Fig. 2.

An increase in cytosolic Ca²⁺ from cellular stores causes a decrease in CFTR-mediated conductance without affecting CFTR single channel activity. a Changes in current were measured using the fast whole cell configuration of the patch clamp technique. Data are plotted as mean changes in conductance plotted relative to the maximum current reached at + 100 mV when cells were perfused with forskolin (fsk). The black trace represents data from cells exposed to thapsigargin (TG; 200 nM) in nominally Ca²⁺-free conditions. The grey trace represents data from cells exposed to thapsigargin in a bath solution containing 1 mM Ca²⁺. b Changes in conductance under the conditions indicated when cells were exposed to thapsigargin in nominally Ca²⁺-free conditions. Conductance was normalised to cell size. Data were analysed from the end of the exposure period to each agonist. Data are mean ± SEM. (n = 7) *p < 0.05 when compared to baseline. ^†p < 0.05 when compared to initial forskolin exposure. c Single channel recordings (on the right) and all points histogram (on the left) used to calculate single channel conductance and open state probability for CFTR at 37 °C in Ca²⁺-free conditions and d after addition of 1.5 mM Ca²⁺ to the cytoplasmic side of the channel. Scale bar represents 10 s interval