Figure 3. AC6^−/− mice present higher blood pH and blood HCO3− under baseline conditions and after 8 days of HCO3− challenge.

To test for a defect in HCO₃⁻ handling, AC6^−/−mice and WT mice were followed for 3 days during baseline conditions and subsequently challenged with HCO₃⁻ (NaHCO₃) loading for 8 days (supplied via drinking water). Because daily water intake is double in AC6^−/− mice, NaHCO₃ was supplied to this genotype at a 50% lower concentration compared with WT mice (0.14 in AC6^−/− mice compared with 0.28 M in WT mice). (A) Water intake during baseline conditions and during HCO₃⁻ loading (n=3 per genotype; one data point is the average of two mice kept in the same cage). (B) Urinary pH during baseline conditions and during HCO₃⁻ challenge (n=6/genotype). (C,D) Blood pH and HCO₃⁻ concentrations under baseline conditions and after 8 days HCO₃⁻ challenge (n=6/genotype). Statistical comparisons in (A,B): *AC6^−/− compared with WT mice (P<0.05); left side of dashed line, ‡baseline day 1 compared with baseline day 2 or 3 in WT mice (P<0.05); right side of dashed line, ^#baseline mean compared with HCO₃⁻ challenge in both genotypes (P<0.05). Statistical comparisons in (C,D): *compared with WT mice or baseline (P<0.05). Statistical comparisons on left and right side of dashed line in (A,B) were performed separately using two-way repeated measurement ANOVAs. Values indicate mean ± S.E.M. Values on bars indicate sample size. Abbreviation: Base, Baseline.