Bioaccumulation, depuration and oxidative stress in fish Carassius auratus under phenanthrene exposure

In this study, laboratory experiment was carried out to determine phenanthrene bioaccumulation, depuration in whole fish and oxidative stress in the liver of freshwater fish Carassius auratus. Fish were exposed to 0.05 mg/l phenanthrene for different periods, while one control group was designated for each exposure group. Some fish after 7 days of exposure were transferred to diluted water. The concentrations of phenanthrene in fish were analyzed by HPLC. Twenty-four hours after the exposure, reactive oxygen species (ROS) were trapped by phenyl-tert-butylnitrone and detected by electron paramagnetic resonance (EPR). The activities of superoxide dismutase (SOD), catalase (CAT), and glutathione-s-transferase (GST) were also determined. The concentrations of phenanthrene in fish increased rapidly shortly after the start of the exposure, reached a maximum level at the 2 days, and then it declined quickly to low-level-steady state. The elimination process of phenanthrene could be divided into two periods-a fast elimination period following a slower loss period. The elimination curve could be fitted mathematically as the sum of two exponential functions according to two-compartment model: C(t)=2.72e(-1.065t) + 0.68e(-0.0364t). The PBN-radical adducts were detected in fish liver samples following the exposure 24h. The hyperfine splitting constants for the PBN-radical adducts were aN = 13.5 G, aH = 1.77 G and g value was 2.0058, which were consistent with those of PBN/()OH. The results indicated that the hydroxyl radical was probably significantly induced during the exposure of phenanthrene, as compared to the control group. The changes of activities of the antioxidant enzymes also were observed. In addition, after fish were removed from phenanthrene exposure, the recovery status of these antioxidant indices was explored. These results clearly indicated phenanthrene could be accumulated in fish and similar redox cyclings were produced, resulting in the changes of the activities of the antioxidant enzymes and the production of ROS with the oxidative stress.