| Summary: | 碩士 === 國立臺灣大學 === 漁業科學研究所 === 96 === In mammal, bicarbonate transporters play an important role in pH regulation, and ten isoforms are grouped into the solute carrier 4 (SLC4) family. Some SLC4 members have been proposed to be associated with ion regulation and acid-base balance in fish, but no convincing evidence is available to support so far. The present study used zebrafish as a model to examine the role of SLC4 members in fish ion regulation and acid/base balance mechanisms. Ten genes of the zebrafish SLC4 have been successfully cloned. Using triple in situ hybridization and/or immunochemistry, 2 novel isoforms, zslc4a1b (zebrafish anion exchanger, zAE1b) and zslc4a4b (zebrafish Na+/HCO3- cotransporter, zNBCe1b), were identified to specifically expressed in the basolateral membrane H+-ATPase rich (HR) cells of zebrafish skin/gills. The preliminary knockdown experiments of the zAE1b and zNBCe1b showed the two novel genes were associated with Na+ uptake and acid-base regulation by qRT-PCR analysis on relevant gene expresions. The qRT-PCR experiments revealed that acclimation to low-Na+ environment up-regulated the mRNA expression of zAE1b, but down-regulated that of zNBCe1b. On the other hand, exposure to acidic freshwater stimulated the zAE1b expression while declined that of zNBCe1b. Taken together, two novel isoforms of zNBC1b and zAE1b were found to specifically express in HR cells of zebrafish, and molecular physiologically demonstrated to be involved in the mechanisms of Na+ uptake/acid-base regulation.
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