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Chloramine-T is a widely used disinfectant in aquaculture for controlling bacterial and parasitic infections. While its antimicrobial efficacy is well established, the sublethal effects of Chloramine-T on fish cardiac tissue are not well understood. This study investigated the impact of short-term Chloramine-T baths on oxidative stress biomarkers and antioxidant defence mechanisms in the hearts of rainbow trout (Oncorhynchus mykiss). The fish were exposed to 9 mg/L chloramine-T in three 20-minute baths, administered at three-day intervals. Cardiac tissue was then analysed for lipid peroxidation (TBARS), protein oxidation (aldehydic and ketonic derivatives of oxidatively modified proteins, OMPs), total antioxidant capacity (TAC) and enzymatic antioxidant activities (SOD, CAT, GR and GPx). Exposure to chloramine-T significantly decreased aldehydic (56.1%) and ketonic (53.9%) protein oxidation products (p < 0.001), while there was a non-significant reduction in lipid peroxidation. Enzymatic antioxidant activities remained largely unchanged, with a mild non-significant increase in SOD and a modest rise in TAC. Correlation and regression analyses revealed a strong correlation between TBARS and OMPs (r = 0.99, p < 0.001) and identified glutathione reductase as the main predictor of lipid peroxidation (β = 0.36, p = 0.04). These results suggest that, at the tested concentration, chloramine-T does not induce harmful oxidative stress in trout hearts, but rather triggers adaptive redox modulation, particularly via glutathione-dependent pathways. These findings provide valuable insights into cardiac redox homeostasis in fish exposed to disinfectants and support the careful therapeutic use of chloramine-T in aquaculture.

 

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