FIGURE 2. H⁺ secretion is reduced in cortical collecting duct cells from Rhcg^−/− mice.

Cortical collecting ducts were isolated from kidneys of Rhcg^+/+ and Rhcg^−/− mice after 2 days of HCl-loading, microperfused in vitro, and intracellular pH (pH_i) monitored. NH₄Cl (20 mM) was applied from the luminal perfusate. (A) Original pH_i tracing from a CCD exposed to a luminal NH₄Cl pulse. The arrow indicates the rate of pH_i change measured and calculated. Exposure to an NH₄Cl pulse caused a large intracellular acidification (not shown) followed by an alkalinization phase leading to pH_i recovery. The initial slope (ΔpHi/Δt) of the alkalinization phase was measured . (B) Bar graph summarizing ΔpHi/Δt after removal of the luminal NH₄Cl pulse (n = 8–12 tubules/genotype). (C) Bar graph summarizing H⁺-fluxes calculated based on intracellular buffering power and pH_i recovery rates.