Effects of Exposure to Sublethal Concentrations of Hexavalent Chromium on the Redox Homeostasis of Periwinkle (Tympanotonos fuscatus Linnaeus)

The imbalance between the rate of production of reactive oxygen species (ROS) and the ability of the body to scavenge harmful free radicals (ROS) results in oxidative stress. Hexavalent chromium (Cr 6+ ) is a toxic oxidation state of chromium that induces oxidative stress at high concentrations. In this study, periwinkles were exposed to sublethal concentrations (0.42, 0.84, and 4.2 mgl -1 ) of Cr 6+  for 30 days while the unexposed animals served as control (0 mgl -1 ). Thereafter, the activities of superoxide dismutase, catalase, and glutathione peroxidase, and the levels of reduced glutathione as well as lipid peroxidation were determined using standard procedures. The results show that there was a concentration-dependent significant increase in the activities of superoxide dismutase, catalase and glutathione peroxidase in the exposed animals compared to the control. The levels of reduced glutathione and lipid peroxidation decreased significantly in the exposed animals compared to the control. The results indicate that exposure to sublethal concentrations of Cr 6+  can modulate redox homeostasis of periwinkles and consequently result in oxidative stress. The stress pattern shown by periwinkles in the presence of chemical stressor, Cr 6+  can be an indicator for chemical pollutant in the environment.