AB 15:261-273 (2012)  -  DOI: https://doi.org/10.3354/ab00427

ABSTRACT: Rainbow trout Oncorhynchus mykiss were pre-treated with silymarin (SMN) to investigate its protective effects on hypoxia/reoxygenation (H/R)-induced pathological and oxidative impacts and on the expression of hypoxia-inducible factor 1α (HIF-1α) and inducible nitric oxide synthase (iNOS) at the mRNA level in the brain and gills of trout. Fifty trout were assigned to control (normoxia) or treatment groups (H/R). The treatment trout were grouped into H/R, which received normal saline, and H/R+S 100, H/R+S 400 and H/R+S 800 treatments, which received 100, 400 and 800 mg SMN, respectively, per kg of fish feed each day for 3 d prior to hypoxia. Hypoxia was induced by bubbling N₂ gas into a water bath, resulting in a lower level of oxygen (5 mg l⁻¹). Fish were kept in a hypoxic condition for 3 h followed by 3 h of normoxia (oxygen level at 10.4 mg l⁻¹), and then blood and tissue were sampled. To evaluate the antioxidant status, the total antioxidant capacity (TAC), malondialdehyde (MDA) content, nitric oxide (NO) level and protein carbonylation rate were assessed in the brain and gills. The expression of HIF‑1α and iNOS mRNA was examined in the brain and gills using semi-quantitative RT-PCR. SMN lowered the H/R-elevated NO, MDA and carbonylated protein levels, while it enhanced the TAC level. Moreover, SMN regulated the H/R up-regulated level of HIF-1α and iNOS in examined tissues. SMN ameliorated the H/R-induced histopathological injuries in the brain and gills. These results suggest that pre-treatment of trout with SMN might be an applicable method for reducing H/R-induced biochemical, histopathological and transcriptional injuries.

KEY WORDS: Hypoxia · Oxidative status · Reoxygenation · Silymarin · Trout