title: Developmental expression of CLC-K1 in the postnatal rat kidney.
abstract: CLC-K1, a kidney-specific chloride channel, has been demonstrated to be involved in the urine concentration mechanism. Here, we investigated the developmental expression of CLC-K1 in the rat kidney. Using immunohistochemistry, we showed that CLC-K1 was not present in the thin ascending limb of Henle's loop during the early prenatal stages but was significantly expressed during the adult stage. CLC-K1 started to appear at day 5 and its expression increased during further development. In developing rats this increase coincided with the increase in the urine-concentrating capacity as the animals matured. We also investigated the expressions of other channels and transporters, including NKCC2, AQP-1, and AQP-2. NKCC2 was strongly expressed throughout the inner medulla in neonatal rat kidneys but was entirely undetectable at the adult stage. The decline in its expression took the form of a gradual recession from the inner medulla together with reciprocal increases in the expression of CLC-K1. AQP-1 was weakly expressed in the inner medulla during early development and showed a rapid increase in expression at a later stage. The collecting duct cells significantly expressed AQP-2 even at birth and maintained its expression throughout the development. These results suggest that CLC-K1 expression is one of the major determinants of the urine-concentrating capacity of the developing rat kidney.
authors.affiliation: Department of Pediatrics, Tokyo Medical and Dental University, School of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi
authors.forename: S
authors.initials: S
authors.lastname: Uchida
authors.forename: S
authors.initials: S
authors.lastname: Mizutani
authors.forename: S
authors.initials: S
authors.lastname: Sasaki
authors.forename: F
authors.initials: F
authors.lastname: Marumo
mesh_terms: D000818:Animals; D051398:Aquaporin 1; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D018118:Chloride Channels / Q000378:metabolism*; D007150:Immunohistochemistry / Q000379:methods; D007668:Kidney / Q000254:growth & development* / Q000378:metabolism*; D007671:Kidney Concentrating Ability / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D028021:Sodium-Potassium-Chloride Symporters
chemical_list: C496022:Aqp1 protein, rat; C496025:Aqp2 protein, rat; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D002352:Carrier Proteins; D018118:Chloride Channels; C082118:Clcnka protein, rat; D028021:Sodium-Potassium-Chloride Symporters; D051398:Aquaporin 1