Alterations in Hepatic Antioxidant Systems and Lipid Peroxidation Products in a Freshwater Fish, Labeo rohita, Exposed to 4-Nonylphenol, an Endocrine Disruptor

4-Nonylphenol (4-NP) is a well-known endocrine-disrupting chemical that could be present in the aquatic environment, but little is known about its oxidative stress effects. An emerging literature suggests that early life exposure to 4-NP may increase the risk of metabolic syndrome. Due to its hydrophobicity and long half-life, 4-NP can easily accumulate in living organisms, including humans, where it inflicts a series of toxic effects. In the present study, the oxidative stress and antioxidant parameters of Labeo rohita after exposure to various sub-lethal concentrations of 4-NP for 5, 10 and 15 days were examined. The level of glutathione content and the activity of glutathione peroxidase and glutathione-s-transferase were significantly inhibited, whereas the activity of superoxide dismutase, catalase and glutathione reductase and the lipid peroxidation products such as malondialdehyde and conjugated diene were significantly elevated, indicating the occurrence of oxidative stress. The results demonstrate that 4-NP in aquatic systems can affect antioxidant responses.