Figure 1.

Buffering capacity of CFPAC-1 human pancreatic duct cells at different pH_i values. Polarized CFPAC-1 cells were exposed to varying concentrations of NH₄Cl (0–30 mmol/L), while Na⁺ and HCO₃^– were omitted from the bath solution to block the Na⁺ and HCO₃^–-dependent pH regulatory mechanisms. β_i was estimated by the Henderson–Hasselbalch equation (n=50). The total buffering capacity (β_total) was calculated as β_total=β_i+β_HCO3^–, where β_HCO3^– is the buffering capacity of the HCO₃^–/CO₂ system. β_HCO3^–=2.3×[HCO₃^–]_i. [HCO₃^–]_i is the intracellular concentration of HCO₃^–.