title: Failure to up-regulate gill Na+,K+-ATPase alpha-subunit isoform alpha1b may limit seawater tolerance of land-locked Arctic char (Salvelinus alpinus).
abstract: Many populations of Arctic char (Salvelinus alpinus) are land-locked, physically separated from the ocean by natural barriers and unable to migrate to sea like anadromous populations. Previous studies which experimentally transferred land-locked Arctic char to seawater report high mortality rates due to osmoregulatory failure and an inability to up-regulate gill Na(+),K(+)-ATPase activity. This study examined the mRNA expression of two recently discovered alpha-subunit isoforms of gill Na(+)K(+)-ATPase (alpha1a and alpha1b) during seawater exposure of land-locked Arctic char. mRNA levels of these gill Na(+),K(+)-ATPasealpha-subunit isoforms were compared to Na(+),K(+)-ATPase activity and protein levels and related to osmoregulatory performance. Land-locked Arctic char were unable to regulate plasma osmolality following seawater exposure. Seawater exposure did not induce an increase in gill Na(+),K(+)-ATPase activity or protein levels. Na(+),K(+)-ATPase isoform alpha1a mRNA quickly decreased upon exposure to seawater, while isoform alpha1b levels were unchanged. These results suggest the inability of land-locked Arctic char to acclimate to seawater is due a failure to up-regulate gill Na(+),K(+)-ATPase activity which may be due to their inability to increase Na(+),K(+)-ATPase alpha1b mRNA expression.
authors.affiliation: Department Integrative Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
authors.forename: J S
authors.initials: JS
authors.lastname: Bystriansky
authors.forename: N T
authors.initials: NT
authors.lastname: Frick
authors.forename: J G
authors.initials: JG
authors.lastname: Richards
authors.forename: P M
authors.initials: PM
authors.lastname: Schulte
authors.forename: J S
authors.initials: JS
authors.lastname: Ballantyne
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000818:Animals; D005618:Fresh Water; D015971:Gene Expression Regulation, Enzymologic; D005880:Gills / Q000201:enzymology*; D007527:Isoenzymes / Q000378:metabolism; D021122:Protein Subunits / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014337:Trout / Q000097:blood / Q000378:metabolism*; D014882:Water-Electrolyte Balance / Q000235:genetics
chemical_list: D007527:Isoenzymes; D021122:Protein Subunits; D012333:RNA, Messenger; D000254:Sodium-Potassium-Exchanging ATPase