Liver oxidative stress of the grey mullet Mugil cephalus presents seasonal variations in Ennore estuary.

The objective of this study was to determine the liver oxidative stress status of grey mullets living in heavy-metal-rich polluted Ennore estuary compared with unpolluted Kovalam estuary. Fish were collected from both estuaries during the monsoon and summer seasons from October 2004 to September 2006. Fish liver homogenate (N = 20 per group) was prepared for evaluating oxidative stress parameters. Fish living in the polluted estuary had significantly higher lipid oxidation products, conjugated dienes (0.346 +/- 0.017 vs 0.141 +/- 0.012 DA233/mg protein), lipid hydroperoxides (0.752 +/- 0.032 vs 0.443 +/- 0.03 nmol/mg protein), and lipid peroxides (3.447 +/- 0.14vs 1.456 +/- 0.096 nmol MDA/mg protein) than those of the unpolluted estuary during the summer. In contrast, significantly lower levels of superoxide dismutase (20.39 +/- 1.14 vs 53.63 +/- 1.48 units/mg protein) and catalase (116 +/- 6.87vs 153 +/- 8.92 units/mg protein) were detected in the liver of fish from the polluted estuary (Ennore) compared to fish from the unpolluted estuary (Kovalam) during the summer. Variations in most of the oxidative stress parameters were observed between the summer and monsoon seasons, indicating the importance of seasonal variation for estuaries and their inhabitants.