| A central composite experimental design with response surface analysis was used to examine the effects of dietary α-tocopherol, ascorbic acid, iron, and selenium on oxidative stress in juvenile chinook salmon. Concentrations of these nutrients in diet ranged from the minimum dietary requirement to levels approaching physiological toxicity. Increasing dietary concentrations of a-tocopherol and ascorbic acid provided enhanced antioxidant protection against tissue peroxidation. Over the ranges tested, neither iron nor selenium concentrations affected oxidative stress. Partially smolted fish sampled in March were more susceptible to oxidative stress and exhibited higher levels of damage to liver lipids compared to parr sampled in December. Physiological changes accompanying the parr-smolt transformation may have been responsible for this difference in susceptibility to oxidative stress, including higher proportions of PUFA in cell membranes, increased cellular metabolism, elevated levels of hormones known to contribute to oxidative stress, or a combination of these factors.; To determine the relationship between the general stress response and oxidative stress, chinook salmon smolts were subjected to a low-water stressor. Fish were sampled at 0 h (unstressed controls; CN) and at 6, 24, and 48 h after the application of low-water stress (ST). In all tissues examined, there was an initial decline in tissue lipid peroxidation (LPO) from the 0-CN to 6-ST (significant for kidney), and a rise in LPO content thereafter to 48-ST in kidney and brain. After 48 h of low-water stress, LPO was significantly higher than in 48-CN for kidney and brain but not liver.; The relationship between dietary lipid source, stress, and oxidative stress was examined in juvenile chinook salmon. Four different experimental diets were used: menhaden oil (MHO; elevated 20:5n-3 and 22:6n-3), soybean oil (SOY; elevated 18:2n-6), linseed oil (LSO; elevated 18:3n-3), and a mixture of 55% linseed oil and 45% soybean oil (MIX; approximately equal levels of 18:2n-6 and 18:3n-3). Fish subjected to a low-water stressor had greater liver and brain LPO compared to unstressed controls; this was not influenced by diet. Diet and stress affected plasma cortisol levels. Stressed fish fed SOY had the greatest cortisol concentrations followed by MIX, MHO, and LSO (mean concentrations for the SOY and LSO diets differed significantly).; The effect of downstream migration on tissue vitamin E, lipid peroxidation, and fatty acid composition in hatchery smolts was examined. Generally, oxidative stress increased (LPO increased and vitamin E decreased) in smolts as they migrated downstream. (Abstract shortened by UMI.)... |
