title: Gene expression and morphological localization of NHE3, NCC and NKCC1a in branchial mitochondria-rich cells of Mozambique tilapia (Oreochromis mossambicus) acclimated to a wide range of salinities.
abstract: We explored molecular and morphological alteration in gill mitochondria-rich (MR) cells of Mozambique tilapia, Oreochromis mossambicus, acclimated to deionized freshwater (DFW), freshwater (FW), 1/3-diluted seawater (1/3 SW) and seawater (SW). Scanning electron microscopic observations revealed that the apical membrane of MR cells appeared as a flat or slightly projecting disk in DFW and FW, being larger in DFW than in FW. In contrast, the apical membrane typically formed a pit structure in 1/3 SW and SW. The mRNA expression levels of Na(+)/H(+) exchanger-3 (NHE3) and Na(+)/Cl(-) cotransporter (NCC) in the gills were increased with decreasing environmental salinity, whereas Na(+)/K(+)/2Cl(-) cotransporter-1a (NKCC1a) expression was upregulated by increasing salinity. Immunofluorescence staining showed that the MR cell population of DFW- and FW-acclimated tilapia consisted mostly of MR cells with apical NHE3 and those with apical-NCC; MR cells with basolateral NKCC1a dominated in SW-acclimated tilapia. These results indicated that apical-NHE3 and apical-NCC MR cells were ion-absorbing cells, and that basolateral-NKCC1a MR cells were ion-secreting cells. In fish acclimated to 1/3 SW, both ion-absorbing and secreting cells existed in the gills, suggesting that fish in near-isotonic water were equipped with mechanisms of both hyper- and hypoosmoregulation to prepare for environmental salinity changes.
authors.affiliation: Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan. niida@marine.fs.a.u-tokyo.ac.jp
authors.forename: Mayu
authors.initials: M
authors.lastname: Inokuchi
authors.forename: Junya
authors.initials: J
authors.lastname: Hiroi
authors.forename: Soichi
authors.initials: S
authors.lastname: Watanabe
authors.forename: Kyung Mi
authors.initials: KM
authors.lastname: Lee
authors.forename: Toyoji
authors.initials: T
authors.lastname: Kaneko
mesh_terms: D000064:Acclimatization; D000818:Animals; D001483:Base Sequence; D005455:Fluorescent Antibody Technique; D005618:Fresh Water / Q000737:chemistry; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D005880:Gills / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D016623:Ion Pumps / Q000235:genetics / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012623:Seawater / Q000737:chemistry; D012965:Sodium Chloride / Q000494:pharmacology*; D049992:Sodium Chloride Symporters / Q000235:genetics / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters / Q000235:genetics / Q000378:metabolism; D013194:Staining and Labeling; D017210:Tilapia / Q000502:physiology*
chemical_list: D016623:Ion Pumps; D012333:RNA, Messenger; D049992:Sodium Chloride Symporters; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D028021:Sodium-Potassium-Chloride Symporters; D012965:Sodium Chloride