title: The impact of different water gas levels on cataract formation, muscle and lens free amino acids, and lens antioxidant enzymes and heat shock protein mRNA abundance in smolting Atlantic salmon, Salmo salar L.
abstract: The present experiment was conducted to examine if freshwater (FW) oxygen and carbon dioxide regimes cause physiological responses that lead to cataract formation in Atlantic salmon (Salmo salar L.) smolt. Duplicate groups of 50 g Atlantic salmon smolts were exposed to three freshwater oxygen saturation regimes (95, 112 or 125% saturation), with or without addition of carbon dioxide (measured 17-18 and 2-3 mg L(-1), respectively), for six weeks before transfer to seawater (SW). The FW exposure groups were followed up for another six weeks under a common SW regime. Fish were screened for cataract and sampled accordingly, at start, after 6 weeks in FW and after 6 weeks in SW. Increased growth related cataract incidences and severities were recorded in SW, mainly in the groups previously exposed to normoxic and hyperoxic conditions in FW, as compared to the respective groups added carbon dioxide. The concentration of histidine compounds (imidazoles) in muscle and lens tissue, used as quantitative risk markers of cataract, were lower than observed in earlier studies, however, neither were affected by the present water gas regimes in FW nor after follow up in SW. Independently of water oxygenation in FW, muscle free amino acid profiles in salmon groups concomitantly exposed to elevated carbon dioxide indicated use of selected free amino acids for energy purposes. Significantly lower abundance of heat shock protein 70 mRNA and trends towards stepwise reduction of antioxidant enzymes mRNA in the lens from fish exposed to increased water oxygenation were recorded, probably linked to increased growth and/or external stress during smoltification. This represents a first communication on using early molecular markers to express reduced protection of the fish lens against external stress to explain cataract development.
authors.affiliation: National Institute of Nutrition and Seafood Research (NIFES), PO Box 2029 Nordnes, N-5817 Bergen, Norway. rune.waagbo@nifes.no
authors.forename: Rune
authors.initials: R
authors.lastname: Waagbø
authors.forename: Camilla Diesen
authors.initials: CD
authors.lastname: Hosfeld
authors.forename: Sveinung
authors.initials: S
authors.lastname: Fivelstad
authors.forename: Pål A
authors.initials: PA
authors.lastname: Olsvik
authors.forename: Olav
authors.initials: O
authors.lastname: Breck
mesh_terms: D000220:Adaptation, Biological; D000596:Amino Acids / Q000032:analysis / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D000975:Antioxidants; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D002245:Carbon Dioxide / Q000494:pharmacology; D002386:Cataract / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D004780:Environment, Controlled; D005393:Fish Diseases / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D005618:Fresh Water / Q000737:chemistry; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D007093:Imidazoles / Q000032:analysis / Q000378:metabolism; D007908:Lens, Crystalline / Q000378:metabolism / Q000503:physiopathology*; D010100:Oxygen / Q000009:adverse effects*; D010313:Partial Pressure; D012333:RNA, Messenger / Q000032:analysis*; D012307:Risk Factors; D020317:Salmo salar / Q000235:genetics / Q000378:metabolism*; D012623:Seawater / Q000737:chemistry
chemical_list: D000596:Amino Acids; D000975:Antioxidants; D015415:Biomarkers; D018840:HSP70 Heat-Shock Proteins; D007093:Imidazoles; D012333:RNA, Messenger; D002245:Carbon Dioxide; D010100:Oxygen