Study On Oxidative Stress Biomarker Of Fish Induced By Nitroaromatic In Water

In the present study, toxicity effects of xylene, p-nitrotoluene, o-nitroaniline andp-nitroaniline of detected contaminations in surface waters were assessed through short-termand long-term exposure for Cyprinus carpio. Cyprinus carpio was exposed to differentdoses of the four compounds. The acute toxicity and joint toxicity were designed to assessthe toxicity effects of the studied chemicals, and a set of biomarkers was employed todetermine the possible biological impacts, such as the antioxidant enzymes, lipid oxidationand other biological indicators in fish liver. The results described as follows:1) Acute toxicities of xylene, p-nitrotoluene, o-nitroaniline and p-nitroaniline to Cyprinuscarpio were35.78mg/L,41.43mg/L,20.42mg/L and49.36mg/L, respectively. Thetoxicity of four nitroaromatic compounds to Cyprinus carpio was moderately toxic, with atoxicity sequence for the studied chemicals of o-nitroaniline﹥xylene﹥p-nitrotoluene﹥p-nitroaniline.2) Joint toxicity experiments showed that the toxicity effects of different binary mixturesof four nitroaromatic compounds to Cyprinus carpio were different. The joint toxicity ofbinary mixtures in equitoxicity ratios and equiconcentration ratios were partly addition orantagonism between p-nitroaniline and p-nitrotoluene. Xylene and p-nitrotoluene toCyprinus carpio displayed antagonistic effect in equitoxicity ratios and equiconcentrationratios. The interaction responses of binary mixtures in equiconcentration ratios andequiconcentration ratios were different that of between o-nitroaniline and p-nitroaniline aswell as xylene and o-nitroaniline. The types of joint effects mainly were additivity for thedifferent tested binary mixtures, so it cannot be ignored that binary mixtures of the testedcompounds may possess potential risk in aquatic ecosystems.3) The results showed that the activities response of SOD, CAT and GPx to nitroanilinecompounds were more sensitive, and that the responses of GST, T-AOC and MDA toxylene were more sensitive. Antioxidant enzymes activities had been inhibited or activatedwhen Cyprinus carpio exposed to o-nitroaniline, p-nitroaniline and xylene. The antioxidantstress responses of biological indicators to above compounds were different.SOD activities were obviously induced previously and then obviously inhibited in allconcentrations of o-nitroaniline compared with control group. With the exposing timeincreasing, the values of SOD activities was V-shaped in1/296hLC₅₀exposed group, meanwhile the increase-decrease law could be seen in other treatments. CAT and GPxactivities were obviously induced when the fish was exposed to1/2、1/4、1/8and1/1696hLC₅₀o-nitroaniline, but no significant differences were observed at concentration of1/25696hLC₅₀when compared to the control（P>0.05）.SOD activities in liver were first induced and then inhibited in five exposureconcentration levels of p-nitroaniline, while CAT activities mainly were significant induced.P-nitroaniline could inhibit the activities of GPx in3d. With the exposing time increasing,GPx activities mainly were induced.The liver CAT activities mainly were significant induced when exposed to differentconcentration of xylene, and CAT activities of1/4and1/896hLC₅₀exposed group werefirst increased and then decreased. T-AOC level of1/16and1/6496hLC₅₀exposed grouponly in6d were significantly higher than control group（P<0.01）, and no significantdifferences were observed at the other time when compared to the control（P>0.05）. Xyleneat exposure concentration could induce the activities of GST. After3¹5d exposure, GSTactivities in1/496hLC₅₀xylene group were notably higher than that of contorl（P<0.01）.GST activities of the other exposed group only in12d and15d were significant induced.Xylene at exposure concentration could cause liver lipid peroxidation in Cyprinus carpio. Inthe highest concentration(1/496hLC₅₀), MDA level increased significantly （P<0.01）. In thelowest concentration(1/6496hLC₅₀), MDA level were not significantly different from thecontrol（P>0.05） at12²1d exposure.There were no synchronization among the activity changes of antioxidant indicators（SOD,CAT, GPx and T-AOC） in liver of Cyprinus carpio when exposed to o-nitroaniline,p-nitroaniline and xylene, while the increase of MDA level were not always associated withthe decrease of antioxidant enzymes activity. Multi-biomarker responses in the liver ofCyprinus carpio when long-term exposure to o-nitroaniline, p-nitroaniline and xylene,suggested that the tested compounds may cause some kinds of damages to the liver ofCyprinus carpio. But there are not concentration limits of above compounds in WaterQuality Standard for Fisheries （GB11607-89）, so the results could provide basic toxicitydata for the revision of Water Quality Standard for Fisheries.