KCa2.2 and KCa2.3 channel open-state kinetics were not changed by extracellular acidosis. Open-time histograms for all single-level openings of both amplitudes at −50 mV from patches containing (A) KCa2.2 in extracellular pH 7.4, (B) KCa2.2 in pH 5.9, (C) KCa2.2(H337N) in pH 7.4, (D) KCa2.3 in pH 7.4, and (E) KCa2.3 in pH 6.6. Distributions were best fit by the sum of two exponentials with τ of 1 and 11 ms for KCa2.2 and 2 and 17 ms for KCa2.3. (F) Mean open times for KCa2.2 and KCa2.3 channel openings at pH 7.4 and 5.9, and those of the mutant KCa2.2 (H337N) channel were plotted against voltage (n = 3). Each open-time component was voltage independent (one-way ANOVA; P > 0.05) and were not affected by lowering the extracellular pH (two-way repeated measures ANOVA; P > 0.05).
