Effects of dietary vitamin E supplementation on antioxidant enzyme activities in Litopenaeus vannamei (Boone, 1931) exposed to acute salinity changes

This study examined the effects of dietary tocopheryl acetate (vitamin E) and salinity on muscle superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) activity and gill Na+/K+-ATPase activity in Litopenaeus vannamei. Three diets containing 0, 100 and 600 mg tocopheryl acetate kg(-1) diet, respectively, were fed to shrimp (40-50 mg) for 35 days. Subsequently, shrimp were subjected to an acute salinity change (30 parts per thousand to 5, 15, 30, and 50 parts per thousand) for 24 h. Significantly (P < 0.05) increased SOD, CAT, GPX and Na+/K+-ATPase activities were observed in shrimp fed diets supplemented with vitamin E compared to shrimp fed the unsupplemented control diet. In addition, when exposed to 5 and 50 parts per thousand, total SOD, CAT and GPX activities of shrimp in all dietary groups were decreased (P < 0.05) compared to shrimp held in 30 parts per thousand, with the exception of SOD in shrimp fed E-600 at 50 parts per thousand and GPX in shrimp fed E-100 at 5 parts per thousand, which did not show a significant decrease (P > 0.05). A similar trend was observed in Na+/K+-ATPase activity of shrimp fed the control diet. Na+/K+-ATPase activity of shrimp fed the vitamin E-supplemented diet showed no significant variation response to acute salinity changes. Supplementation of vitamin E in diet could enhance the resistance of shrimp to acute changes in salinity. However, the higher dose of vitamin E supplement was not significantly different from the moderate dose. The results demonstrated that vitamin E might have a potentially useful role as an effective antioxidant by regulating osmotic balance and resistance to salinity changes in shrimp. (C) 2007 Elsevier B.V All rights reserved.