Oxidative stress among SOD-1 genotypes in rainbow trout (Oncorhynchus mykiss)

Anna Elizabeth Heink

Ozone is commonly used as an oxidizing agent in recirculating hatchery systems to eliminate pathogens and organic solids, however, the physiological costs of chronic ozone exposure in salmonid fishes are not well understood. Natural variation in the antioxidant-enzyme SOD-1 is known to alter the impacts of oxidative damage at both the cellular and organismal levels. Using three clonal lines of rainbow trout, [Hot Creek (n = 30), Arlee (n = 21), and Swanson (n = 10)], all of which contain SNP differences and amino acid substitutions at the SOD-1 locus, this study investigated the functional effects of this variation in terms of SOD activity during ozone stress, and subsequent levels of oxidative damage to DNA and cell membranes. Fish from each line were subjected to a 24 hour period of ozone stress, after which, tissues were analyzed for antioxidant status (liver SOD-1, erythrocyte SOD) and oxidative damage (TBARS in gill tissue and blood plasma, DNA damage). SOD-1 activity in the liver among control and ozonated fish showed downregulation of SOD-1 in the Hot Creek line, and upregulation in the Arlee and Swanson fish. SOD activity in erythrocytes was not significantly upregulated following ozonation, however significant differences were observed among clonal lines overall, driven mainly by lower activity in the Hot Creek line. Ozone had a significant treatment effect in all oxidative damage parameters assessed, as it increased lesioning of DNA in erythrocytes, and levels of lipid peroxidation in gills and plasma. Among lines, Swanson showed significantly higher TBARS levels in gill tissue after ozonation than Arlee or Hot Creek. Swanson control and treatment fish also showed significantly lower TBARS levels in plasma than fish from the other lines. These among-line differences in SOD activity and oxidative damage provide evidence for the hypothesis that SOD-1 genotypes differ functionally in their defense against oxygen stressors such as ozone; linking other biochemical and organismal responses to oxygen stress within this clonal system merits further investigation. Information from this research will be of benefit to aquaculturists in selecting for genotypes which are less susceptible to oxidative damage.

Oxidative stress among SOD-1 genotypes in rainbow trout (Oncorhynchus mykiss)

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