Detoxifying response in juvenile tench fed by selenium diet.

The effects of a selenium (Se) diet (1.0 mg Se kg⁻¹) were investigated on growth, accumulation and antioxidant response in juvenile Tinca tinca at three endpoints (0, 4 and 8 weeks). Growth and condition factor (K>1.5) for both control (0.25 mg Se kg⁻¹) and Se tench were not significantly affected. Se exposed fish exhibited the highest Se level in the kidney and the liver after 4 weeks. By feeding more Se the accumulation capacity of tench did not increase and a plateau, mainly for the liver, was thus reached. Se level remained almost constant in the muscle if compared to own control and for each endpoint. Superoxide dismutase activity in both tissues was not affected by Se supplementation and the higher catalase level in the kidney might support the hypothesis that the enzyme was adequate to remove the hydrogen peroxide production following Se exposure. However, supplemented diet with higher Se level could be critical for tench, as it may cause a lowering of glutathione peroxidase and glutathione reductase activities facilitating the onset of oxidative damage. The enhancement of thiol level and glutathione S-transferase activity, mainly in the liver, could be the signals of the only protection against the oxidative damage induced by Se.