Abstract
The potential of commercial astaxanthin on growth, biochemical factors, and antioxidant-related gene expression following a challenge with diazinon were studied in rainbow trout (Oncorhynchus mykiss). Fish (~ 20.70 g) were fed diets containing commercial astaxanthin (ASX) at 0.00 (CTR and ASX0), 0.50 (ASX1), 2.00 (ASX2), and 5.00 (ASX3) g kg(-1) for 60 days. Afterwards, the treated fish (ASX1, ASX2, ASX3) as well as the fish in ASX0 group were challenged with diazinon (0.11 mg L(-1)) for 96 hr whereas fish in the CTR group was not challenged with diazinon. Results showed that growth pattern improved significantly with all enriched diets compared to the ASX0 group. Metabolic enzyme activities, including alanine aminotransferase and alkaline phosphatase decreased in ASX2 and ASX3 groups with respect to the ASX0 group. Serum antioxidant status also showed the same pattern with enhancement in the fish fed with the ASX2 and ASX3 supplemented diets. Feeding the fish with astaxanthin, particularly in the ASX3 group, up-regulated the expression of some antioxidant-relevant genes, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), and nuclear factor erythroid-2 related factor 2 (Nrf2) in the kidney and liver. Besides, the histopathological damages in kidneys and liver induced by diazinon were less pronounced in the ASX2 and ASX3 groups compared to the ASX0 group. In conclusion, commercial astaxanthin, especially at 5.00 g kg(-1), enhanced the growth performance and ameliorated the oxidative stress induced by diazinon in rainbow trout.