TISSUE-SPECIFIC EFFECT OF MERCURY ON ANTIOXIDANT DEFENSE SYSTEM AND PROTECTIVE ROLE OF SELENIUM ON MERCURY-INDUCED OXIDATIVE STRESS IN BLUE MUSSEL Mytilus galloprovincialis (Lamarck 1819)

摘要

Mercury (Hg), one of the most toxic environmental and industrial pollutants, is receiving increased attention globally because of human health and environmental concerns. In the present study, we investigated the toxic effect of Hg in the absence or presence of selenium (Se) on the antioxidant enzymes in different tissues, such as hepato-pancreas and gills, of mussels M. galloprovincialis after their exposure for 6 days. Mussels were exposed to Hg (25 μg L~(-1) Hg~(2+)), Se (4 μg L~(-1) Se~(4+)) and the mixture (25 μg L~(-1) Hg~(2+) +4 μg L~(-1) Se~(4+)) of the former two elements. Similar effect was found in the activities of superoxide dismutase (SOD) and glutahione peroxidase (GPx) which initially increased and subsequently decreased with the duration of exposure time in hepatopancreas and gills tissues of blue mussels exposed to metals; CAT was significantly inhibited by Hg from 4th day in hepatopancreas but no significant change was found in gills. Activities of antioxidant enzymes in Se-treated mussels were significantly elevated compared with Se-free mussels including control and Hg-treated groups. The result of the statistical evaluation showed that apparent tissue-specific effect was found in antioxidant enzyme activities in mussels exposed to Hg and the induction of key antioxidant defenses as a result of selenium supplementation might play an important role in protection of aquatic organisms against oxidant stress caused by heavy metals.