Localization of Chloride Transporters in Gill Epithelia of the Grass Pufferfish, Takifugu niphobles

Grass pufferfish ( Takifugu niphobles) is a euryhaline species of seawater origin and widely distributed along the western seashore of Taiwan. In order to reveal the basis of Cl- transport mechanisms in gills of this euryhaline species, the immunolocalization of Cl- transporters, i.e., Na+/K+/2Cl- cotransporter (NKCC), cystic fibrosis transmembrane conductance regulator (CFTR), anion exchanger 1 (AE1), and chloride channel 3 (CLC-3) was performed. In order to illustrate the distributions and numbers of those Cltransporters in gill epithelia, the grass pufferfish was acclimated to fresh water (FW) or seawater (SW, 35 ‰) for more than one month, and cryosections of gills were observed and analyzed by the confocal laser scanning microscope after double-immunofluorescent staining of the Cl transporters with Na+/K+-ATPase (NKA). The antibody staining results showed that in gills of grass pufferfish, NKA as well as NKCC, AE1, and CLC-3 were colocalized in the basolateral parts of immunoreactive epithelial cells of FW- or SWacclimated individuals, while CFTR were localized only in the apical sides of NKA immunoreactive cells in SW fish. In FW or SW grass pufferfish, immunoreactive cells were only distributed in gill filaments. This study provided direct in vivo evidence of simultaneous immunolocalization of Cl transporters in gills of SW