isoform expression and cation selectivity change with salinity in salt-secreting epithelia of .

To provide insight into claudin (Cldn) tight junction (TJ) protein contributions to branchial salt secretion in marine teleost fishes, this study examined TJ protein isoforms of a euryhaline teleost (mummichog; ) in association with salinity change and measurements of transepithelial cation selectivity. Mummichogs were transferred from freshwater (FW) to seawater (SW, 35‰) and from SW to hypersaline SW (2SW, 60‰) in a time course with transfer control groups (FW to FW, and SW to SW). FW to SW transfer increased mRNA abundance of and twofold, whilst and transcripts were unchanged.