title: Gene expression of Na+/H+ exchanger in zebrafish H+ -ATPase-rich cells during acclimation to low-Na+ and acidic environments.
abstract: In mammalian nephrons, most of the Na(+) and HCO(3)(-) is reabsorbed by proximal tubular cells in which the Na(+)/H(+) exchanger 3 (NHE3) is the major player. The roles of NHEs in Na(+) uptake/acid-base regulation in freshwater (FW) fish gills are still being debated. In the present study, functional genomic approaches were used to clone and sequence the full-length cDNAs of the nhe family from zebrafish (Danio rerio). A phylogenetic tree analysis of the deduced amino acid sequences showed that zNHE1-8 are homologous to their mammalian counterparts. By RT-PCR analysis and double/triple in situ hybridization/immunocytochemistry, only zebrafish NHE3b was expressed in zebrafish gills and was colocalized with V-H(+)-ATPase but not with Na(+)-K(+)-ATPase, indicating that H(+)-ATPase-rich (HR) cells specifically express NHE3b. A subsequent quantitative RT-PCR analysis demonstrated that acclimation to low-Na(+) FW caused upregulation and downregulation of the expressions of znhe3b and zatp6v0c (H(+)-ATPase C-subunit), respectively, in gill HR cells, whereas acclimation to acidic FW showed reversed effects on the expressions of these two genes. In conclusion, both NHE3b and H(+)-ATPase are probably involved in Na(+) uptake/acid-base regulation in zebrafish gills, like mammalian kidneys, but the partitioning of these two transporters may be differentially regulated depending on the environmental situation in which fish are acclimatized.
authors.affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan, ROC.
authors.forename: Jia-Jiun
authors.initials: JJ
authors.lastname: Yan
authors.forename: Ming-Yi
authors.initials: MY
authors.lastname: Chou
authors.forename: Toyoji
authors.initials: T
authors.lastname: Kaneko
authors.forename: Pung-Pung
authors.initials: PP
authors.lastname: Hwang
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019295:Computational Biology; D004777:Environment; D005786:Gene Expression Regulation; D005880:Gills / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D005810:Multigene Family; D012333:RNA, Messenger / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism*; D015027:Zebrafish
chemical_list: D012333:RNA, Messenger; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; D025262:Vacuolar Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase