Effects of heavy metals on antioxidants and expression of HSP70 in different tissues of Milk fish (Chanos chanos) of Kaattuppalli Island, Chennai, India

• Impact of metals on antioxidant enzymes were done in the fish of Kaattuppalli Island.
• Fish from polluted site revealed intense expression of HSP 70 due to metal stress.
• Biochemical contents showed reduction in the fish organs from polluted region.
• Heavy industrialization responsible for metal loading in the coast of Kaattuppalli.
• Situation is alarming and the pristine coast need to be protected from pollution.

Distribution of heavy metals and its associated oxidative stress, ultrastructure and expression of HSP 70 were studied in varies tissues of Chanos chanos collected from polluted sites compared with the fish collected from less polluted sites of Kaattuppalli Island. The concentrations of copper, lead, zinc, cadmium, manganese and iron were quantified in gills and liver. The results showed marked differences between the two sites as well as significant variations within the tissues. The decreasing trend of metals in the tissues of fish sampled from both polluted and less polluted sites was in the order of Fe>Mn>Zn>Cu>Pb>Cd. Overall, the highest metal concentrations were found in the fish collected from polluted sites. Similarly increase of antioxidant enzymes biomarkers due to heavy metals was also evident in gills and liver of the fish collected from polluted sites. These tissues were further investigated by scanning and electron microscopy and the results were compared with the reference less polluted sites. The presence of large lipid droplets in liver and increase of mucous cells in gills were some of the most noticeable alterations observed and were related to heavy metal contaminants. It is concluded that scanning, ultrastructural and useful of HSP70 biomarkers for heavy metal induced oxidative stress, and demonstrate that precautions need to be taken in polluted sites of Kaattuppalli Island in order to prevent heavy metal pollution that can occur in the future.