二甲苯对锦鲤鱼肝脏抗氧化酶的影响

采用暴露试验方法,研究了不同浓度二甲苯对锦鲤鱼肝脏组织中超氧化物歧化酶和过氧化氢酶的影响。结果表明,不同浓度组二甲苯在暴露期间对锦鲤鱼肝脏SOD活性的影响较小,只有在个别浓度和个别时间段下发生了显著诱导或抑制作用;锦鲤鱼暴露于二甲苯时对CAT活性影响主要表现为诱导作用,但CAT对1/16 96hLC50浓度二甲苯反应较滞后;随着暴露时间的延长,试验15 d后,CAT活性随着暴露浓度的降低而整体呈下降趋势;试验中CAT活性的变化与SOD活性的变化具有一定的同步性：在3 d和15 d时,1/4 96hLC50浓度组的SOD活性受到诱导,CAT活性也受到诱导;在12 d时,1/8 96hLC50浓度组的SOD活性受到抑制,CAT活性也受到抑制。在本次暴露试验中,CAT活性对二甲苯较敏感,从分子水平上反映了污染物对鱼体肝细胞的损伤,也反映了环境中氧化作用的存在,因此,可以考虑其作为水环境中二甲苯早期污染的生物监测指标。     

Differential levels of antioxidants in paraquat-resistant and -susceptible Erigeron canadensis biotypes in Korea

To characterize the biochemical differences in paraquat-resistant and -susceptible biotypes of Erigeron canadensis L. collected from Korea, we investigated the constitutive levels of various antioxidants such as antioxidant enzymes and low molecular weight antioxidants in leaves, as well as after paraquat treatment. The activities of superoxide dismutase, peroxidase, ascorbate peroxidase, and catalase were higher in the paraquat-resistant biotype than in the paraquat-susceptible biotype. Reduced ascorbic acid content was higher in the resistant biotype, but the content of reduced glutathione was higher in the susceptible biotype. These results indicate that one of the paraquat-resistant mechanisms in E. canadensis in the present study might be related to protecting the activities of antioxidant enzymes, such as superoxide dismutase, peroxidase ascorbate peroxidase, and catalase, as well as the contents of low molecular weight antioxidants such as ascorbate and glutathione.     

Effect of methyl parathion and chlorpyrifos on certain biomarkers in various tissues of guppy fish, Poecilia reticulata

Tests of acute toxicity were performed on the most common species of aquarium fish, Poecilia reticulata. Guppies (P. reticulata) were exposed to progressive concentrations of methyl parathion (MP) and chlorpyrifos (CPF); a semi-static method according to guidelines of OECD was used. Tests of acute toxicity were conducted using 10 fish for each separate concentration and for the control group. The results were subjected to probit analysis to determine the 96 h LC₅₀ values. The 96 h LC₅₀ values of MP and CPF to P. reticulata were 8.48 ppm/L (5.98–10.89) and 0.176 ppm/L (0.313–0.224) respectively. In addition, behavioral changes at each concentration were observed for the individual fish. Fish were exposed for 96 h to different sublethal concentrations of MP and CPF (¼ LC₅₀, 1/8 LC₅₀ and 1/10 LC₅₀) and their oxidative stress-induction potential was estimated in brain, liver and gills of fish. MDA content is induced in all tissues but maximum rise was observed in gills (161% and 153% for MP and CPF respectively). With regard to antioxidant defense system (ADS), GSH level decreased in the brain, liver and gills of tissues of MP treated fishes (22%, 6% and 13% respectively) and showed increase in brain and gills CPF treated (23% and 21% respectively). CAT, GST, GR and SOD levels fluctuated in all treatment groups relative to the control. Brain AChE showed dose-dependent inhibition in fish exposed to the higher concentrations reached 45% and 66% for MP and CPF respectively. Collective findings demonstrated that pesticide exposure of fish induced an increase in MDA and fluctuated ADS along with inhibited AChE. These findings may be used as valuable biomarkers for evaluation of water pollution.