Mean traces (+ standard error of the mean) of Isc in (A) Cl- free solution (n=14) and (D) HCO3- free solution (n=10) of primary hAECs cultures (dotted lines represent the time of addition of drugs). Summary of S0859-induced changes in Isc in the presence (B) or absence (E) of HCO3- in primary hAECs cultures and Fsk-induced HCO3- secretion (C) in Cl- free buffer (on panels B, C,, and E, each dot represents an independent experiment; means ± sem are shown next to the individual data; respectively n=17, n=14, and n=11 independent experiments using cells from N=3 donors; two-tailed, paired t-test). (F) Representative pHi trace of primary hAECs bathed first in bilateral HCO3- KRB (gassed with 5% CO2) then bilateral Hepes buffered KRB (no HCO3-, no CO2) and then bilateral HCO3- KRB (gassed with 5% CO2). CO2 removal and re-introduction is marked by a transient increase and decrease in pHi respectively. (G) Representative trace of pHi recovery after CO2-induced acidification in the absence of basolateral HCO3-. (H) Representative trace of pHi recovery after CO2-induced acidification in the absence of basolateral Na+ and HCO3-. (I) Summary of the magnitude of CO2-induced acidification (bilateral bicarbonate, n=7, apical bicarbonate n=14, unpaired t-test, bars represent mean ± standard deviation (S.D.)). (J) Mean percentage of pHi recovery after perfusion of the different solutions (Bilateral Bicarbonate, n=7; Apical Bicarbonate, n=14; Bilateral Bicarbonate after Apical Bicarbonate-, n=5; Na+-free buffer, n=8; Bilateral Bicarbonate after Na+-free buffer, n=8; One-way ANOVA with Holm-Sidak correction for multiple comparison tests, bar graph represents mean ± S.D.). (K) Representative trace of intracellular pH measurements showing recovery from CO2-induced acidification in the presence (red line) or absence (blue line) of NBC inhibitor S0859. (L) Summary of rates of recovery from CO2-induced acidification in the presence of NHE inhibitor (Dimethyl Amiloride, DMA, 100 μM) and in the presence (red bar) or absence (blue bar) of S0859 (30 μM), (n=3, paired t-test; bars represent mean ± S.D.).