title: Differential expression of Na+, K(+)-ATPase α-1 isoforms during seawater acclimation in the amphidromous galaxiid fish Galaxias maculatus.
abstract: Inanga (Galaxias maculatus) is an amphidromous fish with a well-known capacity to withstand a wide range of environmental salinities. To investigate the molecular mechanisms facilitating acclimation of inanga to seawater, several isoforms of the Na(+), K(+)-ATPase ion transporter were identified. This included three α-1 (a, b and c), an α-2 and two α-3 (a and b) isoforms. Phylogenetic analysis showed that the inanga α-1a and α-1b formed a clade with the α-1a and α-1b isoforms of rainbow trout, while another clade contained the α-1c isoforms of these species. The expression of all the α-1 isoforms was modulated after seawater exposure (28‰). In gills, the expression of the α-1a isoform was progressively down-regulated after seawater exposure, while the expression of the α-1b isoform was up-regulated. The α-1c isoform behaved similarly to the α-1a, although changes were less dramatic. Physiological indicators of salinity acclimation matched the time frame of the changes observed at the molecular level. A 24-h osmotic shock period was highlighted by small increases in plasma osmolality, plasma Na(+) and a decrease in muscle tissue water content. Thereafter, these values returned close to their pre-exposure (freshwater) values. Na(+), K(+)-ATPase activity showed a decreasing trend over the first 72 h following seawater exposure, but activity increased after 240 h. Our results indicate that inanga is an excellent osmoregulator, an ability that is conferred by the rapid activation of physiological and molecular responses to salinity change.
authors.affiliation: School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand. mauricio.urbinafoneron@pg.canterbury.ac.nz
authors.forename: Mauricio A
authors.initials: MA
authors.lastname: Urbina
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Schulte
authors.forename: Jason S
authors.initials: JS
authors.lastname: Bystriansky
authors.forename: Chris N
authors.initials: CN
authors.lastname: Glover
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D019295:Computational Biology; D017931:DNA Primers / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics / Q000502:physiology*; D005880:Gills / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009520:New Zealand; D036441:Osmeriformes / Q000378:metabolism / Q000502:physiology*; D010802:Phylogeny; D060888:Real-Time Polymerase Chain Reaction; D054712:Salinity; D012623:Seawater; D017422:Sequence Analysis, DNA; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D017931:DNA Primers; D007527:Isoenzymes; D000254:Sodium-Potassium-Exchanging ATPase