title: Urinary excretion of aquaporin-2 in pathological states of water metabolism.
abstract: Aquaporin-2 (AQP-2) is an arginine vasopressin (AVP)-regulated water channel in renal collecting duct cells. Approximately 3 % of AQP-2 in collecting duct cells is excreted into urine. Urinary excretion of AQP-2 varies widely in different physiological conditions, and it has a positive correlation with plasma AVP levels. Urinary excretion of AQP-2 was significantly increased by the single injection of AVP in patients with central diabetes insipidus. The urinary excretion of AQP-2 was one-eighth over in patients with central diabetes insipidus and three times greater in patients with impaired water excretion than that in normal subjects. In a hypertonic saline test, the urinary excretion of AQP-2 promptly increased 6-12-fold in normal subjects, but remained low in patients with central diabetes insipidus. In addition, exaggerated urinary excretion of AQP-2 persisted after an acute water load in patients with impaired water excretion. These results indicate that urinary excretion of AQP-2 is a potent marker for the diagnosis of water metabolism disorders dependent on AVP.
authors.forename: S
authors.initials: S
authors.lastname: Ishikawa
mesh_terms: D000818:Animals; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins / Q000008:administration & dosage / Q000235:genetics / Q000652:urine*; D015415:Biomarkers / Q000032:analysis; D018849:Controlled Clinical Trials as Topic; D003919:Diabetes Insipidus / Q000150:complications / Q000652:urine; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000652:urine; D006801:Humans; D008103:Liver Cirrhosis / Q000150:complications / Q000652:urine; D008297:Male; D011863:Radioimmunoassay; D012016:Reference Values; D012680:Sensitivity and Specificity; D015854:Up-Regulation; D014867:Water / Q000378:metabolism; D014883:Water-Electrolyte Imbalance / Q000175:diagnosis* / Q000209:etiology / Q000652:urine*
chemical_list: C496023:AQP2 protein, human; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D015415:Biomarkers; D014867:Water