title: Urinary excretion of aquaporin-2 water channel differentiates psychogenic polydipsia from central diabetes insipidus.
abstract: The present study was undertaken to determine whether urinary excretion of aquaporin-2 (AQP-2) water channel under ad libitum water intake is of value to differentiate polyuria caused by psychogenic polydipsia from central diabetes insipidus. A 30-min urine collection was made at 0900 h in 3 groups of: 11 patients with central diabetes insipidus (22-68 yr old), 10 patients with psychogenic polydipsia (28-60 yr old), and 15 normal subjects (21-38 yr old). In the patients with central diabetes insipidus, the plasma arginine vasopressin level was low despite hyperosmolality, resulting in hypotonic urine. Urinary excretion of AQP-2 was 37 +/- 15 fmol/mg creatinine, a value one-fifth less than that in the normal subjects. In the patients with psychogenic polydipsia, plasma arginine vasopressin and urinary osmolality were as low as those in the patients with central diabetes insipidus. However, urinary excretion of AQP-2 of 187 +/- 45 fmol/mg creatinine was not decreased, and its excretion was equal to that in the normal subjects. These results indicate that urinary excretion of AQP-2, under ad libitum water drinking, participates in the differentiation of psychogenic polydipsia from central diabetes insipidus.
authors.affiliation: Department of Medicine, Jichi Medical School, Tochigi, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Saito
authors.forename: S
authors.initials: S
authors.lastname: Ishikawa
authors.forename: T
authors.initials: T
authors.lastname: Ito
authors.forename: H
authors.initials: H
authors.lastname: Oda
authors.forename: F
authors.initials: F
authors.lastname: Ando
authors.forename: M
authors.initials: M
authors.lastname: Higashiyama
authors.forename: S
authors.initials: S
authors.lastname: Nagasaka
authors.forename: M
authors.initials: M
authors.lastname: Hieda
authors.forename: T
authors.initials: T
authors.lastname: Saito
mesh_terms: D000328:Adult; D000368:Aged; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins / Q000652:urine*; D001127:Arginine Vasopressin / Q000097:blood; D015415:Biomarkers / Q000652:urine; D003919:Diabetes Insipidus / Q000175:diagnosis* / Q000652:urine; D003937:Diagnosis, Differential; D004327:Drinking Behavior; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D011863:Radioimmunoassay
chemical_list: C496023:AQP2 protein, human; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D015415:Biomarkers; D001127:Arginine Vasopressin