title: The ClC-3 chloride channel and osmoregulation in the European sea bass, Dicentrarchus labrax.
abstract: Dicentrarchus labrax migrates between sea (SW), brackish and fresh water (FW) where chloride concentrations and requirements for chloride handling change: in FW, fish absorb chloride and restrict renal losses; in SW, they excrete chloride. In this study, the expression and localization of ClC-3 and Na(+)/K(+)-ATPase (NKA) were studied in fish adapted to SW, or exposed to FW from 10 min to 30 days. In gills, NKA-α1 subunit expression transiently increased from 10 min and reached a stabilized intermediate expression level after 24 h in FW. ClC-3 co-localized with NKA in the basolateral membrane of mitochondria-rich cells (MRCs) at all conditions. The intensity of MRC ClC-3 immunostaining was significantly higher (by 50 %) 1 h after the transfer to FW, whereas the branchial ClC-3 protein expression was 30 % higher 7 days after the transfer as compared to SW. This is consistent with the increased number of immunopositive MRCs (immunostained for NKA and ClC-3). However, the ClC-3 mRNA expression was significantly lower in FW gills. In the kidney, after FW transfer, a transient decrease in NKA-α1 subunit expression was followed by significantly higher stable levels from 24 h. The low ClC-3 protein expression detected at both salinities was not observed by immunocytochemistry in the SW kidney; ClC-3 was localized in the basal membrane of the collecting ducts and tubules 7 and 30 days after transfer to FW. Renal ClC-3 mRNA expression, however, seemed higher in SW than in FW. The potential role of this chloride channel ClC-3 in osmoregulatory and osmosensing mechanisms is discussed.
authors.affiliation: Equipe Adaptation Ecophysiologique et Ontogenèse, UMR5119 - EcoSyM, UM2-UM1-CNRS-IRD-IFREMER, cc 092, Place E. Bataillon, 34095 Montpellier cedex 05, France. bossusmaryline@hotmail.fr
authors.forename: Maryline
authors.initials: M
authors.lastname: Bossus
authors.forename: Guy
authors.initials: G
authors.lastname: Charmantier
authors.forename: Eva
authors.initials: E
authors.lastname: Blondeau-Bidet
authors.forename: Bianca
authors.initials: B
authors.lastname: Valletta
authors.forename: Viviane
authors.initials: V
authors.lastname: Boulo
authors.forename: Catherine
authors.initials: C
authors.lastname: Lorin-Nebel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001492:Bass / Q000235:genetics / Q000378:metabolism*; D001921:Brain / Q000378:metabolism; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D005618:Fresh Water; D005880:Gills / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D012623:Seawater; D017422:Sequence Analysis, DNA; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D014882:Water-Electrolyte Balance
chemical_list: D018118:Chloride Channels; C115376:ClC-3 channel; D029941:Fish Proteins; D012333:RNA, Messenger; D000254:Sodium-Potassium-Exchanging ATPase