Toxicological Effects of Lufenuron on Antioxidant Defence in Grass Carp ( <i>Ctenopharyngodon idella</i> )

Lufenuron, an acyl urea insecticide, is widely used in agriculture, but its ecotoxicological impact on freshwater fish remains poorly understood. The present study investigated the biochemical and antioxidant responses of grass carp (Ctenopharyngodon idella) following chronic exposure to sublethal concentrations of lufenuron (2-4 µg/L) for 33 days. A total of 60 fish were randomly distributed into control and treatment groups, and tissues, including liver, kidney, gills, heart and brain, were sampled on Days 11, 22 and 33. Antioxidant enzyme activities-superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and glutathione (GSH)-were quantified spectrophotometrically. Results revealed organ-specific responses to lufenuron exposure. SOD and GSH levels increased significantly (p < 0.05) in all examined tissues, indicating enhanced defence against oxidative stress. In contrast, POD activity declined in the gills and kidney but increased in the liver, brain and heart. CAT activity was elevated in the liver, kidney and gills but decreased markedly in the heart and brain, suggesting tissue-dependent vulnerability to oxidative damage. Overall, the findings demonstrate that lufenuron induces oxidative stress in C. idella, disrupting enzymatic antioxidant defences in detoxifying and non-detoxifying organs. Antioxidant enzymes are thus reliable biomarkers for assessing the ecological risks of pesticide contamination in aquatic environments.