Intestinal Gene Expression of Na + /HCO 3 − cotransporter 1 (nbce1) Isoforms in Atlantic Salmon During Smoltification and Seawater Acclimation

• Published in: The FASEB Journal
• Main Authors: McKay, Ian, Koltenyuk, Victor, Lema, Sean, McCormick, Stephen, Breves, Jason
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2020
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1096/fasebj.2020.34.s1.04877

In preparation for migration from freshwater to marine habitats, Atlantic salmon undergo smoltification, a springtime transformation that includes the development of seawater tolerance. The ability of smolts to inhabit seawater is attained through the coordinated development of ion and water‐transporting processes in key organs such as the gill, kidney, and intestine. To promote solute‐linked water absorption, the intestinal epithelium of fishes acclimated to SW secretes HCO 3 − to form luminal Ca 2+ and Mg 2+ precipitates. As a source of HCO 3 − for apical anion exchange, Na + /HCO 3 − cotransporter 1 (Nbce1) facilitates the transport of plasma HCO 3 − into the interior of epithelial cells across the basolateral membrane. While Atlantic salmon ( Salmo salar ) express three nbce1 isoforms ( nbce1.1 , nbce1.2a , and nbce1.2b ), there is no information on whether their expression corresponds with the development of intestinal fluid absorption that occurs during smoltification. We first determined that nbce1.1 and nbce1.2b gene transcripts were highly expressed in pyloric cacae and anterior intestine of smolts, whereas nbce1.2a showed low expression in the intestine but robust expression in gill. Next, we sampled salmon undergoing parr‐smolt transformation and observed elevated branchial Na + /K + ‐ATPase activity in May characteristic of smoltification. Moreover, smolts exhibited an improved ability to maintain ionoregulatory balance when transferred to seawater in May versus March. We will report corresponding patterns of nbce1.1 and nbce1.2b expression in pyloric cacae and anterior intestine during smoltification and following seawater transfer to resolve whether their transcriptional patterns correspond with the acquisition of intestinal fluid absorptive processes. Support or Funding Information Supported by the National Science Foundation (IOS‐1755131).