title: Decrease in urinary excretion of aquaporin-2 associated with impaired urinary concentrating ability in diabetic nephropathy.
abstract: Aquaporin-2 (AQP-2) is known to be expressed in the renal collecting duct cells and participates in urinary concentration in response to arginine vasopressin (AVP). The present study was undertaken to determine whether progression of renal dysfunction affects urinary excretion of AQP-2 in diabetic nephropathy. The study was composed of 8 control subjects and 14 patients with type 2 diabetes classified into two groups according to serum creatinine level (cut-off point; 1.5 mg/dl). After an 8-hour water deprivation, both urinary osmolality (U(osm)) and urinary excretion of AQP-2 significantly decreased in the diabetic patients with chronic renal failure as compared to the control subjects (p < 0.0001, p < 0.05, respectively). After a water load (10 ml/kg), no differences were found in plasma osmolality (P(osm)), AVP levels and U(osm), whereas urinary excretion of AQP-2 significantly decreased in the patients with chronic renal failure as compared to the control subjects (p < 0.05). These results indicate that the decreased urinary excretion of AQP-2 in diabetic nephropathy is due to the impaired cellular signaling of AVP in collecting duct cells, which may be partly involved in the urinary concentrating defect in renal failure.
authors.affiliation: Department of Medicine, Division of Endocrinology and Metabolism, Jichi Medical School, Tochigi, Japan.
authors.forename: Tomoatsu
authors.initials: T
authors.lastname: Nakamura
authors.forename: Takako
authors.initials: T
authors.lastname: Saito
authors.forename: Ikuyo
authors.initials: I
authors.lastname: Kusaka
authors.forename: Minori
authors.initials: M
authors.lastname: Higashiyama
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Nagasaka
authors.forename: Shun
authors.initials: S
authors.lastname: Ishibashi
authors.forename: San-e
authors.initials: SE
authors.lastname: Ishikawa
mesh_terms: D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins / Q000652:urine*; D001127:Arginine Vasopressin / Q000097:blood / Q000502:physiology; D016022:Case-Control Studies; D003928:Diabetic Nephropathies / Q000503:physiopathology / Q000652:urine*; D006801:Humans; D007671:Kidney Concentrating Ability; D007685:Kidney Tubules, Collecting / Q000503:physiopathology; D008875:Middle Aged; D015398:Signal Transduction
chemical_list: C496023:AQP2 protein, human; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D001127:Arginine Vasopressin