Fig. 11.

Luminal and basolateral Na⁺-dependent pH_i regulation of principal cells (PCs) and intercalated cells (IC) in microperfused isolated collecting ducts (CDs) from control and orpk mutant mice. A: control CD. Simultaneously removing luminal (L) and basolateral (B) Na⁺ caused a small decrease in pH_i (ab). Following an NH₄⁺ prepulse-induced acid load (bcde), there was little pH_i recovery in the continued absence of external Na⁺ (ef), or after returning luminal Na⁺ alone (fg). Subsequently returning basolateral Na⁺ elicited a pronounced increase in pH_i (gh). NaR, Na-Ringer solution. B: orpk CD. The experimental protocol was identical to that shown in A. Removing luminal and basolateral Na⁺ elicited a more pronounced decrease in pH_i (ab). Following the subsequent acid load (bcde) with little pH_i recovery in the absence of luminal and basolateral Na⁺ (ef), returning luminal Na⁺ in the continued absence of basolateral Na⁺ elicited a large increase in pH_i (fg), which was unaffected by then returning basolateral Na⁺ (gh). C: luminal and basolateral Na⁺-stimulated pH_i recovery rates (ΔpH_i/Δt). Using data from panel A- and B-type experiments, the luminal Na⁺ (Na_L)-stimulated ΔpH_i/Δt was calculated from the pH_i recovery at point f in PCs and ICs from control (gray bars) and orpk (black bars) CDs. The basolateral Na⁺ (Na_B)-stimulated ΔpH_i/Δt was calculated from the pH_i recovery at point g in PCs and ICs from control (gray bars) and orpk (black bars) CDs. *P < 0.05 vs control.