Urinary excretion of aquaporin-2 water channel exaggerated dependent upon vasopressin in congestive heart failure

Background. Impaired water excretion occurs in patients with congestive heart failure. The present study was undertaken to determine whether urinary excretion of aquaporin-2 (AQP-2) water channel is exaggerated in patients with congestive heart failure dependent upon arginine vasopressin (AVP). Methods. Sixty-five patients with congestive heart failure and eight age- and gender-matched control subjects were examined. The patients were divided into four groups according to the criteria of New York Heart Association (NYHA). Plasma AVP levels, urinary excretion of AQP-2, and cardiac index were determined. Results. Plasma AVP levels were progressively increased following the severity of NYHA class in the patients with congestive heart failure. Cardiac index was inversely decreased, and there was a negative correlation between plasma AVP levels and cardiac index (r=0.430, P<0.02). Urinary excretion of AQP-2 was 187.3 +/- 50.2 fmol/mg creatinine in the control subjects. It was markedly increased in the patients. Urinary excretion of AQP-2 was elevated to 1144.4 +/- 257.5 and 990.5 +/- 176.0 fmol/mg creatinine in the patients with NYHA class III and class IV, respectively, values significantly greater than the control subjects (P<0.05). Urinary excretion of AQP-2 had a positive correlation with plasma AVP levels (r=0.280, <0.02). Conclusion. The present study indicates that exaggerated urinary excretion of AQP-2 is dependent on baroreceptor-mediated release of AVP in patients with congestive heart failure.