RICHARDS, Jeff G; SEMPLE, Jeff W*; SCHULTE, Patricia M; Univ. of British Columbia, Vancover, British Columbia; Univ. of Waterloo, Waterloo, Ontario; Univ. of British Columbia, Vancouver, British Columbia: Pattern of Na⁺/K⁺ ATPase isoform expression in rainbow trout (Oncorhynchus mykiss) following abrupt seawater transfer

It is well established that increases in Na⁺/K⁺ ATPase activity in gill and intestine are involved in seawater acclimation in salmonids. We identified five isoforms of the Na⁺/K⁺ ATPase alpha subunit in freshwater acclimated rainbow trout using reverse transcription-polymerase chain reaction (PCR). Using isoform specific PCR amplification, we determined that two of the Na⁺/K⁺ ATPase alpha subunit isoforms were present in all tissues examined (brain, eye, gill, heart, liver, kidney, spleen, intestine, white muscle, red muscle, and testis), while the other three isoforms had tissue-specific distributions. One was restricted to the gill and heart, and another was found only in white and red muscle. The fifth isoform was found to be present at high levels in the brain, eye, gill, and kidney. Changes in Na⁺/K⁺ ATPase isoform expression, protein level, and total enzyme activity were examined in the gills, intestine, and kidney of trout for up to 15 d after abrupt transfer from fresh water to 40 or 80% sea water.