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Chloramine-T is a widely used disinfectant for the treatment of gill diseases of fish in freshwater, and more recently attention has turned to its use in seawater. However, despite the wide use of chloramine-T, few studies have examined its toxicity to fish. Therefore, the aim of the current study was to examine the effects of disinfection by Chloramine-T on the muscle tissue of rainbow trout (Oncorhynchus mykiss Walbaum) using oxidative stress biomarkers (levels of 2-thiobarbituric acid reactive substances and derivatives of oxidatively modified proteins) and biochemical enzymes’ activity (alanine- and aspartate aminotransferases (ALT and AST), lactate dehydrogenase (LDH)) to observe the its toxic effects. The endpoints obtained from this study will be useful to monitor the effects of disinfectant bathing with Chloramine-T for this species of fish. In the disinfectant group, rainbow trout (n = 11) were exposed to Chloramine-T in final concentration of 9 mg per L. Control group of trout (n = 11) was handled with water from basin in the same way as Chloramine-T exposed group. Fish were bathed with Chloramine-T for 20 min and repeated three times every 3 days. Two days after the last bathing fish were sampled to study. Our results showed that Chloramine-T bathing caused the decrease of the lipid peroxidation as well as ALT and AST activity and significant decrease of LDH activity (by 339%, p = 0.017) compared to controls. Chloramine-T markedly affects on lactate and pyruvate metabolism and resulted to decrease of LDH activity. Correlative analysis revealed that the lipid peroxidation level is correlated with ALT and AST activity in the muscle tissue of unhandled control group. In the muscle tissue of trout disinfected by Chloramine-T, LDH activity is correlated positively with ALT and AST activity. Thus, the skeletal muscles of fish play an important role in the processing of lactate through the gluconeogenic and glycogenic pathways including a greater potential for biosynthesis. Our studies indicated that Chloramine-T in dose of 9 mg per L could at least partly attenuate oxidative stress and can be used for prophylactic disinfecting treatment of rainbow trout. Oxidative stress and biochemical alterations could be effectively used as potential biomarkers of Chloramine-T toxicity to the fish in the warning signal for pharmaceutical exposure to aquatic organisms. However, more detailed studies on using of these specific biomarkers to monitor the disinfectant treatment in aquaculture are needed.
Key words: Chloramine-T disinfection, rainbow trout (Oncorhynchus mykiss Walbaum), muscle tissue, lipid peroxidation, aminotransferases, lactate dehydrogenase