title: Characterization of gill Na/K-ATPase activity and ouabain binding in Antarctic and New Zealand nototheniid fishes.
abstract: The effects of thermal acclimation in two Nototheniid species, the stenothermal Antarctic Trematomous bernacchii and the eurythermal New Zealand Notothenia angustata, were investigated. Serum osmolality, gill Na/K-ATPase activity, sodium pump density and ouabain affinity were determined. Both fish were acclimated at their upper and lower viable thermal temperatures. Warm acclimation (+4 degrees C) of the T. bernacchii significantly decreased their serum osmolality from 550 to 450 mOsm/kg compared to cold-acclimation (-1.5 degrees C) and this was accompanied by a two-fold increase in gill Na/K-ATPase activity. Warm-acclimation (+14 degrees C) of N. angustata did not significantly change their serum osmolality from 330 mOsm/kg or gill Na/K-ATPase activity compared to the cold-acclimated (+4 degrees C) N. angustata. Using [(3)H]ouabain binding techniques, the B(max) and K(d) values of gill Na/K-ATPase enzymes were determined. No difference in the B(max) or K(d) of the warm-acclimated T. bernacchii accounted for the increase in Na/K-ATPase activity. We conclude that the change in gill Na/K-ATPase activity in the warm-acclimated T. bernacchii is not mediated by an increase in the number of enzyme sites and is not reflected in a change in ouabain affinity for Na/K-ATPase.
authors.affiliation: Department of Biomedical Sciences, Creighton University School of Medicine, 2500 California Plaza, Omaha, NE 68178, USA. sierrag@creighton.edu
authors.forename: Sierra
authors.initials: S
authors.lastname: Guynn
authors.forename: Frank
authors.initials: F
authors.lastname: Dowd
authors.forename: David
authors.initials: D
authors.lastname: Petzel
mesh_terms: D000064:Acclimatization; D000818:Animals; D000864:Antarctic Regions; D005399:Fishes / Q000378:metabolism*; D005880:Gills / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009520:New Zealand; D009994:Osmolar Concentration; D010042:Ouabain / Q000378:metabolism*; D011485:Protein Binding; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
chemical_list: D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase