Molecular characterization and gene expression of Na+-K+-2Cl− cotransporter2 (NKCC2) in the gastrointestinal tract of Olive flounder (Paralichythys olivaceus) during the four days after infection with Streptococcus parauberis

This study reports on the molecular characterization and gene expression of Na+-K+-2Cl− cotransporter2 (NKCC2) in the gastrointestinal tract of Olive flounder Paralichythys olivaceus infected with Streptococcus parauberis. It examines the electroneutral cation-Cl− cotransporter, and NKCC2 expressed in the intestinal tract. First, we isolated cDNA encoding NKCC2 from the intestinal tract of Olive flounder and investigated the tissue distribution pattern of NKCC2 mRNA. Reverse transcription-PCR analysis detected expressions of NKCC2 in the intestine and kidney. A quantitative PCR analysis showed that the expression level of NKCC2 in the anterior and posterior intestines was higher than in the rectum. Second, we performed a challenge experiment comparing physiological saline (PS) and PS plus the bacteria and analyzed the subsequent gene expression of NKCC2. At 4 days after bacterial injection the comparison between treatment and control found that the expression levels of NKCC2 mRNA increased significantly i...