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This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 293/6/C1814    most recent 00358.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Yan, J.-J. Articles by Hwang, P.-P. Search for Related Content PubMed PubMed Citation Articles by Yan, J.-J. Articles by Hwang, P.-P.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Gene expression of Na⁺/H⁺ exchanger in zebrafish H⁺-ATPase-rich cells during acclimation to low-Na⁺ and acidic environments

¹Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan; ²Institute of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan; ³Institute of Fishery Science, National Taiwan University, Taipei, Taiwan, Republic of China; and ⁴Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan

Submitted 10 August 2007 ; accepted in final form 2 October 2007

In mammalian nephrons, most of the Na⁺ and HCO₃^– 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.

ion uptake; acid-base regulation

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