title: Expression of ion transporters in gill mitochondrion-rich cells in Japanese eel acclimated to a wide range of environmental salinity.
abstract: We examined morphological changes and molecular mechanisms of ion regulation in mitochondrion-rich (MR) cells of Japanese eel acclimated to different environmental salinities. Electron microscopic observations revealed that the apical membrane of MR cells appeared as a flat or slightly projecting disk with a mesh-like structure on its surface in eel acclimated to freshwater (FW). In seawater (SW)-acclimated eel, in contrast, the apical membrane of MR cells showed a slightly concave surface without a mesh-like structure. The mRNA expression of Na(+)/H(+) exchanger-3 (NHE3) in deionized FW and normal SW was higher than that in normal FW and 30%-diluted SW. Expression of Na(+)/K(+)/2Cl(-) cotransporter-1a (NKCC1a) became higher with increasing environmental salinity. Immunofluorescence staining showed that the apical NHE3 immunoreaction was stronger in deionized FW and normal SW than in the other groups. Basolateral NKCC1 immunoreaction was most intense in normal SW. These results indicate that apical NHE3 is involved in ion uptake in fish acclimated to hypotonic environments, and that basolateral NKCC1 is important for acclimation to hypertonic environments. The relatively high expression of NHE3 in SW further indicates a possible role of NHE3 in acid-base regulation in the gills in SW-acclimated fish.
authors.affiliation: Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan. myseo@marine.fs.a.u-tokyo.ac.jp
authors.forename: Mi Young
authors.initials: MY
authors.lastname: Seo
authors.forename: Miyuki
authors.initials: M
authors.lastname: Mekuchi
authors.forename: Keitaro
authors.initials: K
authors.lastname: Teranishi
authors.forename: Toyoji
authors.initials: T
authors.lastname: Kaneko
mesh_terms: D000064:Acclimatization; D000811:Anguilla / Q000378:metabolism*; D000818:Animals; D003001:Cloning, Molecular; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D005786:Gene Expression Regulation; D005880:Gills / Q000378:metabolism* / Q000648:ultrastructure; D017136:Ion Transport; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure; D009928:Organ Specificity; D064587:Osmoregulation; D010802:Phylogeny; D021122:Protein Subunits / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D054712:Salinity; D055049:Salt Tolerance; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism; D064506:Solute Carrier Family 12, Member 2 / Q000235:genetics / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism
chemical_list: D029941:Fish Proteins; D021122:Protein Subunits; D012333:RNA, Messenger; D017923:Sodium-Hydrogen Exchangers; D064506:Solute Carrier Family 12, Member 2; D025262:Vacuolar Proton-Translocating ATPases
keywords: Gill; Japanese eel; Mitochondrion-rich cell; NHE3; NKCC1a; Osmoregulation; V-ATPase