Gene expression of Na+/H+ exchanger in zebrafish H+ -ATPase-rich cells during acclimation to low-Na+ and acidic environments.
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.
Yan
Jia-Jiun
JJ
Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan, ROC.
Chou
Ming-Yi
MY
Kaneko
Toyoji
T
Hwang
Pung-Pung
PP
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
D012333:RNA, Messenger; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; D025262:Vacuolar Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase