Table 1.

Blood and urine parameters obtained under the basal, acid-load, and fludrocortisone-treated conditions

Basal ConditionNH4Cl LoadingFludrocortisone
WTV1aR−/−WTV1aR−/−WTV1aR−/−
Blood
    pH7.26 ± 0.017.28 ± 0.017.27 ± 0.057.23 ± 0.017.42 ± 0.01a7.41 ± 0.01a
    Pco2 (mmHg)45.8 ± 1.039.6 ± 1.5b39.8 ± 3.733.0 ± 1.941.9 ± 2.237.8 ± 1.0
    Po2 (mmHg)83.7 ± 2.698.2 ± 3.0b84.0 ± 1.495.6 ± 3.783.2 ± 4.687.2 ± 4.4
    HCO3 (mmol/L)20.4 ± 0.518.6 ± 0.618.5 ± 1.913.9 ± 1.0a,c26.9 ± 0.8a23.9 ± 0.9a
    Na (mmol/L)149.6 ± 0.6150.6 ± 0.7155.0 ± 0.6d151.3 ± 1.3153.0 ± 1.5152.3 ± 1.2
    K (mmol/L)3.79 ± 0.144.26 ± 0.143.57 ± 0.153.90 ± 0.203.28 ± 0.193.17 ± 0.06a
    Cl (mmol/L)111.3 ± 0.7113.7 ± 1.1120.7 ± 1.3a123.3 ± 1.1a106.2 ± 0.6d105.3 ± 2.2a
Urine
    pH6.45 ± 0.036.29 ± 0.035.99 ± 0.02a5.82 ± 0.037a7.00 ± 0.02a7.96 ± 0.36a,b
    titratable acid (μEq/μg Cr)0.11 ± 0.010.15 ± 0.01b0.21 ± 0.01a0.25 ± 0.01a0.04 ± 0.01a0.002 ± 0.002a
    ammonium (μEq/μg Cr)0.16 ± 0.010.13 ± 0.011.79 ± 0.13a1.28 ± 0.08a,b0.24 ± 0.040.39 ± 0.04a
    net acid excretion (μEq/μg Cr)0.27 ± 0.010.28 ± 0.012.01 ± 0.14a1.54 ± 0.08b0.28 ± 0.040.41 ± 0.04
  • V1aR−/− mice showed low plasma bicarbonate and Pco2 levels in addition to an increased plasma potassium concentration, indicating the presence of type 4 renal tubular acidosis. The NH4Cl load showed that V1aR−/− mice have decreased ability to excrete urinary ammonium. Fludrocortisone ameliorated metabolic acidosis and hyperkalemia mainly by increasing the urinary excretion of ammonium in V1aR−/− mice. Mean ± SEM. n = 6.

  • aP < 0.01 and dP < 0.05 versus wild-type or V1aR−/− in the basal condition.

  • bP < 0.01 and cP < 0.05 versus wild-type mice in each condition.