Fig. 6.

Effect of chloride and bicarbonate substitution in the bath solution on ATP-inducible clamp current in mpkCCD_c14 cells. A: superimposed I_clamp traces of cell monolayers bathed in regular Krebs-Henseleit solution (solid trace) or in Krebs-Henseleit solution in which chloride (Cl⁻) and bicarbonate (HCO₃⁻) were replaced with gluconate and HEPES (dashed trace). Amiloride indicates addition of amiloride (10⁻⁵ M) to the apical bath; V_te indicates clamp of transepithelial voltage to −50 mV; ATP indicates addition of ATP (10⁻⁶ M) to the apical bath. B: superimposed I_clamp traces of cell monolayers bathed in regular Krebs-Henseleit solution (solid trace) or in Krebs-Henseleit solution in which Cl⁻ and HCO₃⁻ were replaced with sulfate and HEPES (dashed trace). C: quantitation of I_clamp values in response to apical addition of ATP to cell monolayers bathed in regular Krebs-Henseleit solution (Reg KHS), in KHS in which Cl⁻ and HCO₃⁻ were replaced with gluconate and HEPES (Cl⁻ free), or in KHS in which Cl⁻ and HCO₃⁻ were replaced with sulfate and HEPES (Cl⁻/Gluc-Free; n = 12 filters). *P < 0.05.