author(s)
Sahar Saleem Lahori, Kaleem Ullah, Muhammad Zaman Baig, Fatima Khan, Aqsa Mubeen Shoukat, Umer Liaqat, Hammad Hassan and Filza Ghafoor

abstract
Nanoparticles are the essential components of the environment that affect the natural aquatic ecosystem and human beings. Every aerobic organism possesses antioxidant defense system to avoid the oxidative stress. Research was designed to check the changes in catalase and peroxidase activities in different fish organs (liver, gills, kidney, and muscles) of Cyprinus carpio after acute exposure of copper nanoparticles. Fish seed for trial was collected from natural breeding ponds. Copper nanoparticles were prepared by co-precipitation method and characterized by different techniques such as Transmission electron microscopy, Scanning electron microscopy, FT-IR, X- ray diffraction method (XRD) and UV-Visible spectroscopy. The LC₅₀ of Cu nanoparticle was checked after 96-hr acute exposure by probit analysis method. Copper nanoparticles induced time dependent alterations in the catalase and peroxidase activities, as the time increased the activities of these enzymes also increased. After acute exposure, the catalase activity showed different results in fish organs liver > gills > kidney > muscles, also the results of peroxidase that observed during acute exposure was liver > gills > kidney > muscles. The findings concluded that the toxicity mechanism of Cu nanoparticle, may be due to the oxidative stress caused by these particles. Physio-chemical parameters were also measured. Data was statistically analyzed by ANOVA and correlation.