Na+/HCO3 − cotransporter 1 (nbce1) isoform gene expression during smoltification and seawater acclimation of Atlantic salmon

AbstractThe life history of Atlantic salmon (Salmo salar) includes an initial freshwater phase (parr) that precedes a springtime migration to marine environments as smolts. The development of osmoregulatory systems that will ultimately support the survival of juveniles upon entry into marine habitats is a key aspect of smoltification. While the acquisition of seawater tolerance in all euryhaline species demands the concerted activity of specific ion pumps, transporters, and channels, the contributions of Na+/HCO3− cotransporter 1 (Nbce1) to salinity acclimation remain unresolved. Here, we investigated the branchial and intestinal expression of threeNa+/HCO3− cotransporter 1 isoforms, denotednbce1.1,-1.2a, and-1.2b. Given the proposed role of Nbce1 in supporting the absorption of environmental Na+ by ionocytes, we first hypothesized that expression of a branchialnbce1 transcript (nbce1.2a) would be attenuated in salmon undergoing smoltification and following seawater exposure. In two separate years, we observed spring increases in branchial Na+/K+-ATPase activity,Na+/K+/2Cl− cotransporter 1, andcystic fibrosis transmembrane regulator 1 expression characteristic of smoltification, whereas there were no attendant changes innbce1.2a expression. Nonetheless, branchialnbce1.2a levels were reduced in parr and smolts within 2  days of seawater exposure. In the intestine, gene transcript abundance fornbce1.1 increased from spring to summer in the anterior intestine, but not in ...
Source: Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology - Category: Physiology Source Type: research