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This Article Full Text Full Text (PDF) Supplemental Tables All Versions of this Article: 296/6/R1897    most recent 00029.2009v1 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 PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Liao, B.-K. Articles by Hwang, P.-P. PubMed PubMed Citation Articles by Liao, B.-K. Articles by Hwang, P.-P.

WATER AND ELECTROLYTE HOMEOSTASIS

Expression regulation of Na⁺-K⁺-ATPase 1-subunit subtypes in zebrafish gill ionocytes

¹Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan; and ²Institute of Zoology, National Taiwan University Taipei, Taiwan

Submitted 18 January 2009 ; accepted in final form 3 April 2009

In zebrafish (Danio rerio), six distinct Na⁺-K⁺-ATPase (NKA) 1-subunit genes have been identified, and four of them, zatp1a1a.1, zatp1a1a.2, zatp1a1a.4, and zatp1a1a.5, are expressed in embryonic skin where different types of ionocytes appear. The present study attempted to test a hypothesis of whether these NKA 1 paralogues are specifically expressed and function in respective ionocytes. Double fluorescence in situ hybridization analysis demonstrated the specific expression of zatp1a1a.1, zatp1a1a.2, and zatp1a1a.5 in NKA-rich (NaR) cells, Na⁺-Cl^– cotransporter (NCC)-expressing cells, and H⁺-ATPase-rich (HR) cells, respectively, based on the colocalization of the three NKA 1 genes with marker genes of the respective ionocytes (epithelial Ca²⁺ channel in NaR cells; NCC in NCC cells; and H⁺-ATPase and Na⁺/H⁺ exchanger 3b in HR cells). The mRNA expression (by real-time PCR) of zatp1a1a.1, zatp1a1a.2, and zatp1a1a.5 were, respectively, upregulated by low-Ca²⁺, low-Cl^–, and low-Na⁺ freshwater, which had previously been reported to stimulate uptake functions of Ca²⁺, Cl^–, and Na⁺. However, zatp1a1a.4 was not colocalized with any of the three types of ionocytes, nor did its mRNA respond to the ambient ions examined. Taken together, zATP1a1a.1, zATP1a1a.2, and zATP1a1a.5 may provide driving force for Na⁺-coupled cotransporter activity specifically in NaR, NCC, and HR cells, respectively.

mitochondrion-rich cells; ion regulation; osmoregulation; fish