The effect of different dietary inclusion levels of rutin (a flavonoid) on some liver enzyme activities and oxidative stress indices in rainbow trout, Oncorhynchus mykiss (Walbaum) exposed to Oxytetracycline

The study was conducted using a completely randomized design with five treatments each with three replicates. In each treatment, 30 fish (10 per replicate) with an average body weight of 30 +/- 0.6g were randomly allocated to 60-L tanks. Treatments consisted of a control (a diet without rutin and oxytetracycline (OTC)), an OTC treatment (a diet free from rutin and containing 75mgkg(-1) body weight OTC) and the (OTC+rutin) treatments including diets with different levels of rutin, 500 (R-500+OTC), 1000 (R-1000+OTC) and 2000 (R-2000+OTC) ppm and 75mgkg(-1) body weight per day OTC which were fed to fish for 28days. The aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities in the blood serum after the OTC treatment were significantly (P<0.05) higher than in the control. After the three (OTC+rutin) treatments, the AST and ALT activities were not significantly different from the control. The level of glucose in the blood serum was significantly lower (P<0.05) in all treatments as compared to the OTC treatment. Superoxide dismutase (SOD) and catalase (CAT) activities in red erythrocyte lysates were significantly (P<0.05) reduced after OTC treatment in comparison with the control. After the three (OTC+rutin) treatments, the values of these indices were significantly (P<0.05) higher than the OTC treatment, in particular for the R-1000+OTC treatment. It seems that rutin, as a non-enzymatic inhibitor, is capable of preventing damage to the liver tissue and reducing oxidative stress.