Vacuolar-type H(+)-ATPase and Na+, K(+)-ATPase expression in gills of Atlantic salmon (Salmo salar) during isolated and combined exposure to hyperoxia and hypercapnia in fresh water.
Changes in branchial vacuolar-type H(+)-ATPase B-subunit mRNA and Na+, K(+)-ATPase alpha- and beta-subunit mRNA and ATP hydrolytic activity were examined in smolting Atlantic salmon exposed to hyperoxic and/or hypercapnic fresh water. Pre-smolts, smolts, and post-smolts were exposed for 1 to 4 days to hyperoxia (100% O2) and/or hypercapnia (2% CO2). Exposure to hypercapnic water for 4 days consistently decreased gill vacuolar-type H(+)-ATPase B-subunit mRNA levels. Salmon exposed to hyperoxia had either decreased or unchanged levels of gill B-subunit mRNA. Combined hyperoxia + hypercapnia decreased B-subunit mRNA levels, although not to the same degree as hypercapnic treatment alone. Hyperoxia generally increased Na+, K(+)-ATPase alpha- and beta-subunit mRNA levels, whereas hypercapnia reduced mRNA levels in presmolts (beta) and smolts (alpha and beta). Despite these changes in mRNA levels, whole tissue Na+, K(+)-ATPase activity was generally unaffected by the experimental treatments. We suggest that the reduced expression of branchial vacuolar-type H(+)-ATPase B-subunit mRNA observed during internal hypercapnic acidosis may lead to reduction of functional V-type H(+)-ATPase abundance as a compensatory response in order to minimise intracellular HCO3- formation in epithelial cells.
Seidelin
M
M
Institute of Biology, University of Southern Denmark-Main Campus, Odense University, Campusvej 55, DK-5230 Odense M, Denmark.
Brauner
C J
CJ
Jensen
F B
FB
Madsen
S S
SS
D000222:Adaptation, Physiological; D000818:Animals; D001639:Bicarbonates / Q000032:analysis; D002245:Carbon Dioxide / Q000378:metabolism*; D005618:Fresh Water; D015971:Gene Expression Regulation, Enzymologic; D005880:Gills / Q000201:enzymology*; D010100:Oxygen / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020317:Salmo salar / Q000378:metabolism* / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*
D001639:Bicarbonates; D012333:RNA, Messenger; D002245:Carbon Dioxide; D006180:Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D010100:Oxygen