Figure 8.

Localization of Na⁺/H⁺ exchangers in CFPAC-1 cells. The figure shows representative pH_i traces. A: After exposure to NH₄⁺ in the absence of Na⁺ on both sides of the duct cells, pH_i reduced to 6.73 ± 0.03 (n = 12), and stabilized at this level. We could not detect any active H⁺-pumps in CFPAC-1 cells, since pH_i did not increase in the absence of extracellular Na⁺. Upon addition of Na⁺ to the apical or the basolateral side prompted the pH_i to recover towards the resting values (n = 6-10); B: The administration of 300 µmol/L amiloride (dashed line) to the Na⁺-free (from 2 min before the addition of Na⁺) and Na⁺-containing HEPES solutions prevented the recovery of pH_i in the presence of Na⁺ (n = 6). Removal of amiloride resulted in the recovery of pH_i to resting values.