FIGURE 7.
Mutations in CFTR alter the GTPγS-induced secretory response in AM. Secretion was stimulated by the intracellular introduction of 400 μm GTPγS through the patch clamp pipette. A, whole cell capacitance recordings were obtained with an EPC-9 computer-controlled patch clamp amplifier (HEKA Electronik, Lambrecht, Germany) running PULSE software (HEKA). The EPC-9 includes a built-in data acquisition interface (ITC-16, Instrutech, NY). The software package controlled the stimulus and data acquisition for the software lock-in amplifier in the sine + dc mode. The temporal resolution of the capacitance data were 40 ms/point with a 1-kHz, 20-mV sine wave. The holding potential in the capacitance experiments was −10 mV. All electrophysiological experiments were performed at room temperature. A comparison of averaged secretory responses in voltage-clamped AMs over time was performed. The gray shading over the smooth line represents the S.E. of the average membrane capacitance increase as a function of mutant CFTR genotype over time. Cell number (number of mice used in parenthesis) in the WT experiments was 6(4); ΔF508 was 12(6); G551D was 6(3); cftr−/− KO was 3(2), and in the bafilomycin (BAF) experiments was 4(1). B, summary of the average change in membrane capacitance as well as percent change in membrane capacitance increase as a function of cell genotype. C, data summary of the time to initial secretory response thresholded at 100 fF.