Meeting Abstract

P1.146  Sunday, Jan. 4  Presence of a freshwater and a seawater isoform of Na+,K+-ATPase in the gills of a teleost fish. MCCORMICK, Stephen D.*; CHRISTENSEN, Arne K.; REGISH, Amy; USGS, Conte Anadromous Fish Research Center, Turners Falls, MA; Univ. of Massachusetts, Amherst; USGS, Conte Anadromous Fish Research Center, Turners Falls, MA mccormick@umext.umass.edu

The sodium pump, Na+,K+-ATPase (NKA) in the gills of teleost fish is involved in ion regulation in both fresh water and seawater. The main catalytic subunit of NKA is the α subunit, and recent molecular studies indicate isoforms of this subunit may be differentially regulated by environmental salinity. We have developed and validated antibodies specific to the NKA α-1a and NKA α-1b isoforms of Atlantic salmon, and used Western blots and immunohistochemistry to characterize their size, abundance and localization. The abundance of gill NKA α-1a was higher in fresh water than in seawater, whereas NKA α-1b was more abundant after seawater acclimation. NKA α-1a was present in most chloride cells in fresh water on both the filament and lamellae, but largely absent in seawater chloride cells. NKA α-1b was present in a small number of filamental chloride cells in fresh water (that were distinct from cells with NKA α-1a), but was found in all of the large filamental chloride cells in seawater. The results provide evidence for salinity-specific isoforms of Na+,K+-ATPase that may have distinct functions for ion uptake and secretion. Preliminary data on the regulation of these subunits by cortisol will also be presented.