title: Salt-losing nephropathy in mice with a null mutation of the Clcnk2 gene.
abstract: The basolateral chloride channel ClC-Kb facilitates Cl reabsorption in the distal nephron of the human kidney. Functional mutations in CLCNKB are associated with Bartter's syndrome type 3, a hereditary salt-losing nephropathy. To address the function of ClC-K2 in vivo, we generated ClC-K2-deficient mice.
  
  
  
  ClC-K2-deficient mice were generated using TALEN technology.
  
  
  
  ClC-K2-deficient mice were viable and born in a Mendelian ratio. ClC-K2-/- mice showed no gross anatomical abnormalities, but they were growth retarded. The 24-h urine volume was increased in ClC-K2-/- mice (4.4 ± 0.6 compared with 0.9 ± 0.2 mL per 24 h in wild-type littermates; P = 0.001). Accordingly, ambient urine osmolarity was markedly reduced (590 ± 39 vs. 2216 ± 132 mosmol L-1in wild types; P < 0.0001). During water restriction (24 h), urinary osmolarity increased to 1633 ± 153 and 3769 ± 129 mosmol L-1in ClC-K2-/- and wild-type mice (n = 12; P < 0.0001), accompanied by a loss of body weight of 12 ± 0.4 and 8 ± 0.2% respectively (P < 0.0001). ClC-K2-/- mice showed an increased renal sodium excretion and compromised salt conservation during a salt-restricted diet. The salt-losing phenotype of ClC-K2-/- mice was associated with a reduced plasma volume, hypotension, a slightly reduced glomerular filtration rate, an increased renal prostaglandin E2 generation and a massively stimulated renin-angiotensin system. Clckb-/- mice showed a reduced sensitivity to furosemide and were completely resistant to thiazides.
  
  
  
  Loss of ClC-K2 compromises TAL function and abolishes salt reabsorption in the distal convoluted tubule. Our data suggest that ClC-K2 is crucial for renal salt reabsorption and concentrating ability. ClC-K2-deficient mice in most aspects mimic patients with Bartter's syndrome type 3.
authors.affiliation: Institute of Physiology, University of Regensburg, Regensburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Grill
authors.affiliation: Institute of Physiology, University of Regensburg, Regensburg, Germany.
authors.forename: I M
authors.initials: IM
authors.lastname: Schießl
authors.affiliation: Institute of Physiology, University of Regensburg, Regensburg, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Gess
authors.affiliation: Institute of Physiology, University of Regensburg, Regensburg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Fremter
authors.affiliation: Institute of Physiology, University of Regensburg, Regensburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Hammer
authors.affiliation: Institute of Physiology, University of Regensburg, Regensburg, Germany. hayo@castrop.com.
authors.forename: H
authors.initials: H
authors.lastname: Castrop
mesh_terms: D000818:Animals; D001477:Bartter Syndrome / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D018118:Chloride Channels / Q000235:genetics* / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism; D005919:Glomerular Filtration Rate / Q000235:genetics; D007668:Kidney / Q000378:metabolism / Q000503:physiopathology*; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D010641:Phenotype; D012084:Renin-Angiotensin System / Q000235:genetics*
chemical_list: D018118:Chloride Channels; C489933:Clcnka protein, mouse; D015232:Dinoprostone
keywords: Bartter's syndrome; Clckb; chloride channels; gene targeting