title: Pseudobranch and gill Na(+), K(+)-ATPase activity in juvenile chinook salmon, Oncorhynchus tshawytscha: developmental changes and effects of growth hormone, cortisol and seawater transfer.
abstract: The teleost pseudobranch is a gill-like structure often fused to the anterior of the opercular cavity. Pseudobranch cells are mitochondria rich and have high levels of Na(+), K(+)-ATPase activity. In this study, pseudobranch Na(+), K(+)-ATPase activity in juvenile chinook salmon (Oncorhynchus tshawytscha) was compared to gill Na(+), K(+)-ATPase activity, a known marker of parr-smolt transformation, in three experiments. In two stocks of New Zealand chinook salmon, pseudobranch Na(+), K(+)-ATPase activity was found to significantly increase during development. At these times gill Na(+), K(+)-ATPase activity was also elevated. Pseudobranch Na(+), K(+)-ATPase activity did not increase 10 days after transfer from fresh water to 34 ppt seawater, a treatment that resulted in a twofold increase in gill Na(+), K(+)-ATPase activity. Cortisol (50 microg/g) and ovine growth hormone (5 microg/g) implants had no effect on pseudobranch Na(+), K(+)-ATPase activity in underyearling chinook salmon, while gill Na(+), K(+)-ATPase activity was stimulated by each hormone. In yearling chinook salmon, only cortisol stimulated pseudobranch Na(+), K(+)-ATPase activity 14 days post-implantation. It was concluded that the pseudobranch differs from the gill in terms of the regulation of Na(+), K(+)-ATPase activity and a role during adaptation to seawater is likely to be limited.
authors.affiliation: Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand. michael.quinn@stonebow.otago.ac.nz
authors.forename: Michael C J
authors.initials: MC
authors.lastname: Quinn
authors.forename: Philip A
authors.initials: PA
authors.lastname: Veillette
authors.forename: Graham
authors.initials: G
authors.lastname: Young
mesh_terms: D000367:Age Factors; D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D005618:Fresh Water; D005880:Gills / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D013006:Growth Hormone / Q000494:pharmacology; D006854:Hydrocortisone / Q000097:blood / Q000494:pharmacology; D007150:Immunohistochemistry; D012474:Salmon / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis / Q000378:metabolism*
chemical_list: D013006:Growth Hormone; D000254:Sodium-Potassium-Exchanging ATPase; D006854:Hydrocortisone