| Polycyclic aromatic hydrocarbons?PAHs?is a kind of common environmental organic pollutants.Phenanthrene?Phe?is a simple tricyclic PAHs model compound,Benzopyrene?BaP?is a typical five-ring PAHs representative compound.Both Phe and BaP have multiple toxic effects on biology and ecological environment.Taking Misgurnus anguillicaudatus as the research object,the acute toxic effects of Phe and BaP on Misgurnus anguillicaudatus were studied by static water test,enzyme-linked immunosorbent assay?Elisa?,real-time quantitative PCR and other experimental methods,including 24 h,48 h,72 h,96 h semi-lethal concentration and safety concentration.At the same time,the basis of acute toxicity,the effects of Phe and BaP on antioxidant enzyme activity,gonadal index?GSI?,vitellogenin?VTG?activity and mRNA expression of Misgurnus anguillicaudatus were analyzed and compared.The results are as follows:1.Acute toxicity to Misgurnus anguillicaudatusThe median lethal concentration(LC50)of Phe to Misgurnus anguillicaudatus at 24h,48 h,72 h,and 96 h were 71.37 mg·L-1?41.18 mg·L-1?25.41 mg·L-1?15.24 mg·L-1,the safe concentration?SC?were 3.26 mg·L-1.Phe is highly toxic to Misgurnus anguillicaudatus.The median lethal concentration(LC50)of BaP to Misgurnus anguillicaudatus at 24h,48 h,72 h,and 96 h were 56.90?g·L-1,42.55?g·L-1,33.54?g·L-1,26.66?g·L-1,the Safe concentration?SC?were 6.81?g·L-1.BaP is highly toxic substance to Misgurnus anguillicaudatus.2.Effects on Misgurnus anguillicaudatus antioxidant enzymesUnder the concentration of 1.33 mg·L-1,1.76 mg·L-1,2.34 mg·L-1,3.10 mg·L-11 Phe and 1.47?g·L-1,2.16?g·L-1,3.16?g·L-1,4.64?g·L-1BaP,respectively,they were treated for 7 d,14 d,21 d and 28 d,respectively.The activities of superoxide dismutase?SOD?and catalase?CAT?in the liver of Misgurnus anguillicaudatus increased at first and then decreased with the increase of the concentration of Phe and BaP and the prolongation of exposure time.Both Phe and BaP had certain oxidative toxicity to Misgurnus anguillicaudatus,and the oxidative toxicity of Phe and BaP increased gradually with the increase of concentration and exposure time.BaP exposure group reached the maximum activity of SOD and CAT faster than Phe exposure group.After reaching the maximum activity of SOD and CAT,the decrease rate of SOD and CAT activity in BaP exposure group was faster than that in Phe exposure group.Compared with Phe,BaP exposure group,the oxidative toxicity of SOD and CAT to Loach was stronger,and the activities of SOD and CAT were more sensitive to BaP.3.Effect on Misgurnus anguillicaudatus gonad indexUnder the exposure of Phe test solution and BaP test solution,the GSI of male Misgurnus anguillicaudatus decreased significantly with the increase of the concentration of Phe and BaP and the prolongation of exposure time,while the GSI of female Misgurnus anguillicaudatus increased significantly with the increase of Phe and BaP concentration and exposure time.Both Phe and BaP can inhibit the testicular development of male Misgurnus anguillicaudatus and promote the ovarian development of female Misgurnus anguillicaudatus,have certain estrogenic effects.However,the effect of BaP on the GSI changes of male and female Misgurnus anguillicaudatus was stronger than that of Phe.4.Effect on VTG content in Misgurnus anguillicaudatusUnder the exposure of Phe test solution and BaP test solution,the content of VTG in serum of male and female Misgurnus anguillicaudatus increased significantly,and the content of VTG in testis of male Misgurnus anguillicaudatus and ovary of female Misgurnus anguillicaudatus increased in different degrees.The content of VTG in Misgurnus anguillicaudatus had obvious dose-effect and time-effect relationship with the concentration of Phe and BaP and the exposure time.Both Phe and BaP can induce VTG synthesis in male Misgurnus anguillicaudatus and increase the synthesis of VTG in female Misgurnus anguillicaudatus,which has estrogenic toxicity.Because BaP has more benzene rings and molecular weight,and its own structure is more complex,it has better penetration to the cell membrane,so its estrogenic effect is stronger than Phe.5.Effect on the expression level of vtg mRNA in the liver of male Misgurnus anguillicaudatusIn the test solution environment with Phe concentrations of 1.33 mg·L-11 and 3.10mg·L-11 and BaP concentrations of 1.47?g·L-11 and 4.64?g·L-1,male Misgurnus anguillicaudatus was treated separately 7 d,14 d,21 d,28 d,QPCR method was used to detect the expression of vtg gene mRNA in the liver.After 7 days of exposure to low concentration of Phe and BaP test solution,it was found that there was no significant difference in the expression of vtg gene mRNA between the control group and the control group.Low concentration and low exposure time of Phe and BaP test solution had little effect on the expression of vtg gene mRNA of Misgurnus anguillicaudatus,and the estrogenic toxicity was relatively low.After 28 days of exposure to high concentration of Phe and BaP test solution,the expression of vtg gene mRNA was significantly different from that of the control group.High concentration and long exposure time of Phe and BaP test solution had a great effect on the expression of vtg gene mRNA of Misgurnus anguillicaudatus,and the estrogenic toxicity also increased rapidly.The expression of vtg gene mRNA in Misgurnus anguillicaudatus had obvious dose-effect and time-effect relationship with the concentration of Phe and BaP and the exposure time.At the same time,compared with the Phe test solution,BaP has more estrogenic toxicity and stronger estrogenic effect on Misgurnus anguillicaudatus,so the change of mRNA expression of vtg gene in male Misgurnus anguillicaudatus is more obvious. |
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