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Research Project
AQUAculture infrastructures for EXCELLence in European Fish research
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Acute Stress and an Electrolyte-Imbalanced Diet, but Not Chronic Hypoxia, Increase Oxidative Stress and Hamper Innate Immune Status in a Rainbow Trout (Oncorhynchus mykiss) Isogenic Line
Publication . Magnoni, Leonardo J.; Novais, Sara C.; Eding, Ep; Leguen, Isabelle; Lemos, Marco F. L.; Ozório, Rodrigo O. A.; Geurden, Inge; Prunet, Patrick; Schrama, Johan W.
In aquaculture, fish may be exposed to sub-optimal rearing conditions, which generate
a stress response if full adaptation is not displayed. However, our current knowledge of
several coexisting factors that may give rise to a stress response is limited, in particular
when both chronic and acute stressors are involved. This study investigated changes in
metabolic parameters, oxidative stress and innate immune markers in a rainbow trout
(Oncorhynchus mykiss) isogenic line exposed to a combination of dietary (electrolyteimbalanced diet, DEB 700 mEq Kg−1
) and environmental (hypoxia, 4.5 mg O2 L
−1
)
challenges and their respective controls (electrolyte-balanced diet, DEB 200 mEq Kg−1
and normoxia, 7.9 or mg O2 L
−1
) for 49 days. At the end of this period, fish were
sampled or subjected to an acute stressor (2 min of handling/confinement) and then
sampled. Feeding trout an electrolyte-imbalanced diet produced a reduction in blood
pH, as well as increases in cortisol levels, hepato-somatic index (HSI) and total energy
content in the liver. The ratio between the lactate dehydrogenase (LDH) and isocitrate
dehydrogenase (IDH) activities decreased in the liver of trout fed the DEB 700 diet,
but increased in the heart, suggesting a different modulation of metabolic capacity by
the dietary challenge. Several markers of oxidative stress in the liver of trout, mainly
related to the glutathione antioxidant system, were altered when fed the electrolyteimbalanced diet. The dietary challenge was also associated with a decrease in the
alternative complement pathway activity (ACH50) in plasma, suggesting an impaired
innate immune status in that group. Trout subjected to the acute stressor displayed
reduced blood pH values, higher plasma cortisol levels as well as increased levels of
metabolic markers associated with oxidative stress in the liver. An interaction between diet and acute stressor was detected for oxidative stress markers in the liver of trout,
showing that the chronic electrolyte-imbalance impairs the response of rainbow trout
to handling/confinement. However, trout reared under chronic hypoxia only displayed
changes in parameters related to energy use in both liver and heart. Taken together,
these results suggest that trout displays an adaptative response to chronic hypoxia.
Conversely, the dietary challenge profoundly affected fish homeostasis, resulting in an
impaired physiological response leading to stress, which then placed constraints on a
subsequent acute challenge.
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Funding agency
European Commission
Funding programme
FP7
Funding Award Number
262336