Meeting Abstract
Atlantic salmon (Salmo salar) face the challenge of transition from freshwater to seawater during downstream migration. Prior to migration, salmon undergo the parr-smolt transformation during which they acquire seawater tolerance due largely to an upregulation of gill ion transport proteins. Much is known about transcriptional changes in the gill, however few studies have examined post-translational mechanisms involved in the regulatory response to seawater challenge in salmon. We examined activation of the Na-K-Cl cotransporter (NKCC) in the gills of Atlantic salmon in response to pharmacological stimulation in vitro, and to seawater challenge in vivo. Exposure of gill tissue to 25 µM forskolin resulted in rapid phosphorylation of NKCC as detected by SDS-PAGE followed by Western immunoblotting using an anti-phospho NKCC antibody. In a separate study, Atlantic salmon smolts acclimated to brackish water, were transferred to seawater and sampled after 0, 1, 4, 8, 24, and 72 hours. Plasma osmolality and chloride levels were elevated relative to controls 1 hour post-transfer to seawater, peaked at 8 hours, and subsequently exhibited a decline towards control levels. Despite high levels of gill NKCC protein, we did not detect a change in NKCC phosphorylation in response to acute seawater challenge. Our results suggest that rapid activation of pre-existing NKCC in the gill is not part of the regulatory response to acute seawater challenge in this species.
