Oxidative Stress Responses of a Freshwater Teleost, Anabas testudineus , to an Endocrine Disruptor, Bisphenol A

Abstract

Bisphenol-A (BPA), an industrial chemical used to manufacture polycarbonate plastic, is considered as a potent estrogenic endocrine disruptor. A majority of xenobiotics exert their toxic effect by causing generation of reactive oxygen species, leading to oxidative stress. Reports regarding oxidative stress responses to BPA in fish are scanty. From this viewpoint, in the present study, a freshwater fish, Anabas testudineus , was exposed to sub-lethal concentrations of BPA (2.5, 5.0,&7.5 mg/l), for different time periods (7, 15&30 days). Four major enzymes of the fish's antioxidant defense system viz., catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (Se-GPx), and glutathione-S-transferase (GST), and the non-enzymatic antioxidant glutathione (GSH) were chosen as biomarkers to examine the effects of BPA. The activities of SOD, GPx and GSH were elevated to significant levels, while CAT and GST activities were decreased significantly suggesting oxidative stress in BPAexposed fish. Reactive oxygen species are known to cause DNA fragmentation. Hence, DNA fragmentation assay was also done. The severity of DNA fragmentation in fish exposed to 7.5 mg/L BPA (30days) was remarkably increased (p<0.05 vs control) and this was revealed in gel electrophoresis analysis also. The results clearly show that BPA is a pollutant with oxidative potential, also with a potential for DNA fragmentation. The potential risks of this compound to nature and human populations are significant since the production of BPA related compounds is increasing dramatically each year.