Effects of transportation stress on antioxidation, immunity capacity and hypoxia tolerance of rainbow trout (Oncorhynchus mykiss)

Abstract

Transportation is common and necessary in aquaculture practice. A series of physiological changes in fish are caused by transportation stress. The present study investigated the effects of transportation of rainbow trout Onchorhynchus mykiss. Juvenile rainbow trout were placed in plastic bags, and sampled before transportation (P1), two hours after transportation (P2) and 48 h after transportation (P3). The water temperature, dissolved oxygen (DO), ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3--N) and nitrite nitrogen (NO2–-N) were analyzed. The relative expression of genes involved in stress and immunity (IL-1β, IL-8, TNF-α, LYZⅡ, HSP70 and HSP90), hypoxia tolerance (hif-1α, GLUT-1) and NF-kB pathway related (NF-kB, Ikb and Ikb2) were analyzed by RT-QPCR. In addition, oxidative damage, antioxidant and immune parameters (the activity of malondialdehyde MDA, superoxide dismutase SOD, catalase CAT and total antioxidant capacity T-AOC, acid phosphatase ACP, alkaline phosphatase AKP and total nitric oxide synthase NOS) were determined. The level of DO at P2 point was significantly decreased compared with P1 and P3 point. The NH4+-N concentration was significantly higher than that at P1 and P3. Further, there was a significant increase in HSP70 expression in gill and muscle during transportation. The expression of TNF-α, IL-1 β and IL-8 in gill and IL-1 β and IL-8 in muscle were significantly up regulated during transportation. The HSP70/90, TNF-α, IL-1 β and IL-8 genes can be used as bio-indicators to monitor stress. Moreover, ACP enzyme activity in liver and muscle, AKP in gill and MDA contents in gill and muscle were significantly higher at P2. The activity of NOS and T-AOC in gill was significantly higher at P3, and showed an increasing trend. In general, this study provides basial information of transportation, and will be helpful to choose more suitable conditions for successful transportation of juvenile rainbow trout.