title: The lamellae-free-type pseudobranch of the euryhaline milkfish (Chanos chanos) is a Na(+), K(+)-ATPase-abundant organ involved in hypoosmoregulation.
abstract: In teleosts, the pseudobranch is hemibranchial, with a gill-like structure located near the first gill. We hypothesized that the pseudobranch of the milkfish might exhibit osmoregulatory ability similar to that of the gills. In this study, the obtained Na(+), K(+)-ATPase (NKA) activity and protein abundance profiles showed that these parameters were higher in the pseudobranchs of the seawater (SW)- than the freshwater (FW)-acclimated milkfish, opposite the situation in the gills. The pseudobranch of the milkfish contained two types of NKA-immunoreactive cells, chloride cells (CCs) and pseudobranch-type cells (PSCs). To further clarify the roles of CCs and PSCs in the pseudobranch, we investigated the distributions of two ion transporters: the Na(+), K(+), 2Cl(-) cotransporter (NKCC) and the cystic fibrosis transmembrane conductance regulator (CFTR). NKCC on the basolateral membrane and CFTR on the apical membrane were found only in pseudobranchial CCs of SW-acclimated individuals. Taken together, the results distinguished NKA-IR CCs and PSCs in the pseudobranch of milkfish using antibodies against NKCC and CFTR as markers. In addition, increases in the numbers and sizes of CCs as well as in NKA expression observed upon salinity challenge indicated the potential roles of pseudobranchs in hypo-osmoregulation in this euryhaline teleost.
authors.affiliation: Department of Life Sciences, National Chung Hsing University, Taichung 402, Taiwan.
authors.forename: Sheng-Hui
authors.initials: SH
authors.lastname: Yang
authors.affiliation: Department of Life Sciences, National Chung Hsing University, Taichung 402, Taiwan.
authors.forename: Chao-Kai
authors.initials: CK
authors.lastname: Kang
authors.affiliation: Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei 100, Taiwan.
authors.forename: Hsiu-Ni
authors.initials: HN
authors.lastname: Kung
authors.affiliation: Department of Life Sciences, National Chung Hsing University, Taichung 402, Taiwan; Department of Biological Science and Technology, China Medical University, Taichung 404, Taiwan. Electronic address: thlee@email.nchu.edu.tw.
authors.forename: Tsung-Han
authors.initials: TH
authors.lastname: Lee
mesh_terms: D000064:Acclimatization; D000818:Animals; D043344:Chordata / Q000254:growth & development*; D005618:Fresh Water; D005880:Gills / Q000201:enzymology*; D054712:Salinity; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000378:metabolism; D014882:Water-Electrolyte Balance
chemical_list: D000254:Sodium-Potassium-Exchanging ATPase
keywords: Cystic fibrosis transmembrane conductance regulator; Milkfish; Na(+) K(+), 2Cl(−) cotransporter; Na(+) K(+)-ATPase; Osmoregulation; Pseudobranch