Abstract
The effects of H2O2 were evaluated in the estuarine worm Laeonereis acuta (Polychaeta, Nereididae) collected at the Patos Lagoon estuary (Southern Brazil) and maintained in the laboratory under controlled salinity (10 psu diluted seawater) and temperature (20 degrees C). The worms were exposed to H2O2 (10 and 50 microM) for 4, 7, and 10 days and the following variables were determined: oxygen consumption, catalase (CAT) and glutathione peroxidase activity in both the supernatant and pellet fractions of whole body homogenates. The concentrations of non-protein sulfhydryl and lipid peroxides (LPO) were also measured. The oxygen consumption response was biphasic, decreasing after 4 days and increasing after 7 and 10 days of exposure to 50 microM H2O2 (P < 0.05). At the same H2O2 concentration, CAT activity was lower (P < 0.05) in the pellet fraction of worms exposed for 10 days compared to control. Non-protein sulfhydryl concentration and glutathione peroxidase activity were not affected by H2O2 exposure. After 10 days, LPO levels were higher (P < 0.05) in worms exposed to 50 microM H2O2 compared to control. The reduction in the antioxidant defense was paralleled by oxidative stress as indicated by higher LPO values (441% compared to control). The reduction of CAT activity in the pellet fraction may be related to protein oxidation. These results, taken together with previous findings, suggest that the worms were not able to cope with this H2O2 concentration.
Highlights
Hydrogen peroxide (H2O2) is a non-radical reactive oxygen species and the most stable intermediate in the four-electron reduction of O2 to water
Since H2O2 is uncharged, it passes through cell membranes by diffusion, and when inside the cells it can react with transition metals liberating hydroxyl radicals (HO) [2]
The existence of antioxidant defenses and oxidative stress generation under exposure to pro-oxidants such as H2O2 have been reported in marine organism, with an increase in lipid peroxide (LPO) content [1], induction of antioxidant www.bjournal.com.br enzymes (CAT, superoxide dismutase) [2] and a reduction in oxygen consumption [2,4,5]
Summary
Hydrogen peroxide (H2O2) is a non-radical reactive oxygen species and the most stable intermediate in the four-electron reduction of O2 to water. Bianchini are recipients of CNPq research fellowships. The existence of antioxidant defenses and oxidative stress generation under exposure to pro-oxidants such as H2O2 have been reported in marine organism, with an increase in lipid peroxide (LPO) content [1], induction of antioxidant www.bjournal.com.br enzymes (CAT, superoxide dismutase) [2] and a reduction in oxygen consumption [2,4,5].
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