Fig. 3.

Increased Na⁺-stimulated pH_i regulation across the apical membrane of cilium-deficient vs. cilium-competent CCD principal cell monolayers. A: cilium-competent monolayer. 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 apical Na⁺ alone (fg). Subsequently returning basolateral Na⁺ elicited a pronounced increase in pH_i (gh). B: cilium-deficient monolayer. The experimental protocol was identical to that described for A. Returning apical Na⁺ in the continued absence of basolateral Na⁺ elicited a large increase in pH_i (fg), which was further stimulated by also returning basolateral Na⁺ (gh). C: pH_i dependence of apical Na⁺-induced acid extrusion. Total acid extrusion was plotted for cilium-competent and -deficient monolayers from segment-fg pH_i recoveries in panel A/B-type experiments; n ≥ 3 for each symbol.