ToxSci Advance Access originally published online on July 11, 2003
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Toxicological Sciences 75, 309-313 (2003)
Copyright © 2003 by the Society of Toxicology
ENVIRONMENTAL TOXICOLOGY |
Effects of Salinity on the Uptake, Biotransformation, and Toxicity of Dietary Seleno-L-Methionine to Rainbow Trout


* Environmental Toxicology Program, University of California, Riverside, California 92521, and
Institute of Zoology, Moldovan Academy of Sciences, Chisinau, Moldova
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 57 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.
Key Words: selenium; selenomethionine; salinity; flavin-containing monoxygenase; glutathione; oxidative stress.