title: Effects of salinity on the uptake, biotransformation, and toxicity of dietary seleno-L-methionine to rainbow trout.
abstract: Selenium (Se) is an element that has been of environmental concern in aquatic systems that drain arid regions heavily used for agricultural purposes. As hypersaline conditions are associated with these ecosystems, this study examined the effect of hypersaline water on the uptake, biotransformation, and toxicity of seleno-L-methionine (SeMe) in juvenile rainbow trout. Fish were acclimated for 5 days to four different salinity regimes (0.5, 6.3, 11.9, 16.8 deciSiemens (dS/m) per meter. To mimic arid agricultural runoff solutes, the water was reconstituted with ions found in drainage water of the San Joaquin River in California. Following 7 days of dietary exposure to 180 mg/kg SeMe, mortality, as well as hepatic selenium concentrations and reduced:oxidized glutathione ratios were measured. Hypersaline conditions protected fish from dietary SeMe toxicity. Fish exposed to 0.5 dS/m water experienced 100% lethality in 2.5 days, whereas fish acclimated to 16.8 dS/m water-only experienced 16.7% mortality, which took 5-7 days to occur. There were no significant differences in hepatic selenium concentrations, but diminishment of reduced glutathione:oxidized glutathione (GSH:GSSG) ratios was observed in SeMe-treated fish held in 0.5 dS/m water. SeMe inhibited flavin-containing monoxygenase catalyzed trimethylamine oxidase activity, but salinity failed to induce expression in trout, indicating an oxygenation of organoselenides may play a minor role in SeMe toxicity.
authors.affiliation: Environmental Toxicology Program, University of California, Riverside, California 92521, USA. daniel.schlenk@ucr.edu
authors.forename: Daniel
authors.initials: D
authors.lastname: Schlenk
authors.forename: Natalia
authors.initials: N
authors.lastname: Zubcov
authors.forename: Elena
authors.initials: E
authors.lastname: Zubcov
mesh_terms: D000818:Animals; D001711:Biotransformation; D004032:Diet; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics* / Q000633:toxicity; D005978:Glutathione / Q000032:analysis / Q000378:metabolism; D019803:Glutathione Disulfide / Q000032:analysis / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D008136:Longevity / Q000187:drug effects*; D017686:Oncorhynchus mykiss; D018384:Oxidative Stress; D010105:Oxygenases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012643:Selenium / Q000032:analysis / Q000378:metabolism; D012645:Selenomethionine / Q000493:pharmacokinetics* / Q000633:toxicity; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D012965:Sodium Chloride; D012645:Selenomethionine; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming); D005978:Glutathione; D012643:Selenium; D019803:Glutathione Disulfide