Fig. 4.

Inhibition of sAC and PKA reduces ${\mathrm{HCO}}_3^{-}$-activated apical Cl⁻ permeability. A: effect of the weak sAC agonist ${\mathrm{HSO}}_3^{-}$ (20 mM) on apical Cl⁻ permeability. Bisulfite solutions were prepared by adding 20 mM NaHSO₃ directly to Cl⁻-free and ${\mathrm{HCO}}_3^{-}$-rich solutions. Equimolar Na-gluconate was added to all other solutions. Osmolality was within ±5 mosmol/kgH₂O for all solutions. Breaks in the trace indicate periods of Cl⁻-free wash (at least 5 min). B: summary data for A. ^#Significantly different from BR (n = 5, P < 0.05). Inset: independent experiments comparing apical Cl⁻ permeability in ${\mathrm{HCO}}_3^{-}$-free Ringer solution (BF) with or without ${\mathrm{HSO}}_3^{-}$ (BS). C: inhibition of ${\mathrm{HCO}}_3^{-}$-activated apical Cl⁻ permeability by the PKA inhibitor Rp-adenosine 3′,5′-cyclic monophosphorothioate (Rp-cAMP[S]; 50 μM). D: summary data for C. ^#Different from BR (n = 5, P < 0.05). Inset: independent experiments comparing apical Cl⁻ permeability in ${\mathrm{HCO}}_3^{-}$-free Ringer solution with or without Rp-cAMP[S].