Free Radical Generation And Oxidative Damage In Carassius Auratus Liver As Affected By 2, 4, 6-trichlorophenol

Molecular biomarkers due to their sensitivities in early warning to indicate biological damages following the long-term exposure with low concentrations of the pollutants, have been widely used in ecological risk assessment of water compartments, and becoming one of the hotspots in ecotoxicological studies. In this paper, 2,4,6-trichlorophenol were selected as the toxic pollutants. Laboratory experiments were carried out and electron paramagnetic resonance (EPR) was used to study the free radical generation and antioxidant changes after fish were both intraperitoneally injected and exposed to the pollutants. The aim of this study is to reveal the toxic mechanisms in the organisms induced by the pollutants on the molecular level through studying the mechanisms of oxidative damage and to select the sensitive biomarkers. All that we have done is to try to get early-warning biomarkers under the stress of 2,4,6-TCP. The main results were as follows:1. Direct evidence of free radical generation in fish liver after fish were intraperitoneally injected and exposed with 2,4,6-TCP were provide. The hyperfine splitting constants for the PBN-radical adducts are a^N = 15.3 G, a^H = 3.8 G, g value is 2.0058 and a^N = 13.5 G, a^H = 3.3 G, g value is 2.0058 respectively, which are consistent with those of PBN/ CH3 and PBN/ OCH3. Because OH can react with dimethyl sulphoxide (DMSO) to yield CH3 and OCH3, so it can be considered that the free radical generated in the liver of Carassius auratus was OH.2. Secondary spin trapping technique was used after fish exposure to different concentration and different time periods of 2,4,6-TCP to study the free radical generation, changes of antioxidant defense and relationship with accumulating 2,4,6-TCP in liver. Result showed, OH was significantly induced when 2,4,6-TCP concentration was at the concentration of China fishery security. SOD activity and GSH content were sensitive to 2,4,6-TCP, and were induced significantly at low concentration (0.005 mg l-1), so they have the potential to be used as the biomarker of 2,4,6-TCP.3. The possible pathway for OH generation was as follows: 2,4,6-TCP was oxidized by H₂O₂ in vivo to form phenoxyl radical under the catalytic action of cellular peroxidase, phenoxyl radical oxidized NADH to NAD in the presence of NADH, NAD reacted with oxygen in vivo to produce O₂^-, O₂^-was spontaneously dismutated by SOD to form H₂O₂ and O₂, creating a renewable supply of H₂O₂ as the initiators of the chain reactions until NADH was consumed, and simultaneously, O₂^- reacted with H₂O₂ to form OH radical via Haber-Weiss reaction.