Effect of α-tocopherol on antioxidant enzyme activities and lipid peroxidation in rainbow trout (Oncorhynchus mykiss)

In this study, the effect of α-tocopherol on the antioxidant capacity of rainbow trout (Oncorhynchus mykiss) was determined. For this purpose, activities of antioxidant enzymes such as catalase (CAT), peroxidase (POD) and glutathione reductase (GSSG-Rx) were investigated. Enzyme activities were measured at 0 (control), 1, 3 and 5 h after α-tocopherol injection. In addition, the levels of malondialdehyde (MDA) as a lipid peroxidation marker were determined in the erythrocytes. The results showed that α-tocopherol significantly activated the CAT, POD and GSSG-Rx enzymes as compared with the enzyme activities found in the controls (p < 0.05). However, MDA levels were significantly decreased by α-tocopherol treatment (p < 0.05). The results suggest that α-tocopherol may have a pro-oxidant tendency at a high dose and cause mild oxidative stress which could modulate signal transduction cascades, redirect gene expression, and influence many cellular responses such as proliferation, differentiation, and reproduction. For this reason, α-tocopherol should be used carefully in all applications in relation to fish