Effects Of BDE-209 On Physiological And Biochemical Indexes Of Juvenile Grass Carp(Ctenopharyngodon Idellus)

Decabromodiphenyl ether(BDE-209)is the most widely used and most representative polymer bromine-containing flame retardant in China.It is a persistent organic pollutant because it is difficult to be degraded in the environment.It can enter the water environment through soil infiltration,rainwater leaching,and further accumulates into the human body along the biological chain,thus posing a threat to human life and health.Grass carp(Ctenopharyngodon idellus),as one of the four major domestic fishes in China,has become a common economic animal in freshwater fisheries due to its strong environmental adaptability and high economic value.Therefore,in this experiment,BDE-209 was used as the target poison,and the grass carp juvenile fish was used as the exposed object,and the toxic effects of BDE-209 on the grass carp juvenile fish were comprehensively described in two ways: in vitro exposure and in vivo exposure.In vitro exposure test was set up in the control group and 0.04 μg/L,4 μg/L,400 μg/L three BDE-209 concentration group,liver tissue,brain tissue at different temperatures(15 ° C,25 ° C,35 ° C)After incubation for 60 min,the oxidative kinase and the nervous system enzyme index were determined.The living exposure group was set to the control group and the four BDE-209 exposure groups of 0.05 μg/L,1 μg/L,20 μg/L,and 400 μg/L were exposed.Sampling at 3,7,15,and 31 days,and measuring five indicators including morphology,nervous system,oxidative stress,cytochrome enzyme gene and estrogen receptor gene,and comprehensively evaluating BDE-209 pairs by two experimental methods.The toxic effects of juvenile grass carp and screening for biomarkers that can identify the toxicity of BDE-209 are of great significance for protecting the aquatic environment,developing fishery production,and developing fishery water quality indicators.The results are as follows:1.The effect of in vitro exposure to BDE-209 on the toxicity of grass carp juveniles: The SOD and CAT activities induced by BDE-209 in the low temperature group were not significantly different from those in the control group,and the MDA content in the high concentration group was increased.The SOD and CAT activities in the normal temperature group had a low concentration of BDE-209 to induce high concentration inhibition.The high temperature group BDE-209 significantly inhibited the CAT,SOD and activity in the liver tissue,and the MDA content in the normal temperature group and the high temperature group.There is an increase,and the activity of AChE increases with the concentration at low temperature,and the activity increases first and then decreases at normal temperature and high temperature,and NOS activity is opposite.The results of this study showed that BDE-209 had no significant effect on the toxicity of grass carp at low temperature;high temperature enhanced the toxic effects of BDE-209 against antioxidant system and nervous system.2.The results of morphological indicators in living exposure test: At the initial stage of BDE-209 exposure,there was no significant change in hepatosomatic index(HIS)of grass carp in each concentration group;at 31 days,HSI of 1 ug/L,20 ug/L,400 ug/L BDE-209 concentration group decreased significantly;and during the whole period of BDE-209 exposure,there was no significant change in relative fatness(CF)of grass carp in each concentration group.Detection of enzyme activity in nervous system: The activity of AChE was inhibited by exposure to BDE-209,and the short-term exposure to NOS increased.After 31 days exposure,NOS decreased significantly,suggesting that exposure to BDE-209 caused nervous system damage in juvenile grass carp.2.The results of oxidative stress test showed that with the increase of exposure concentration and days of BDE-209,the activities of SOD and CAT of antioxidant enzymes increased,and the content of MDA increased significantly,which indicated that BDE-209 could cause oxidative damage to juvenile grass carp Under the toxicity of BDE-209,the genes related to antioxidant stress also responded in a short time,that is,in a dose-effect relationship.The oxidative damage was reduced by up-regulating the expression of sod1,cat,hsp70,hsp90,MT and so on.The damage of low concentration BDE-209 to fish body could not cause the change of gene level in a short time.However,after long exposure to BDE-209,the expression of antioxidant gene increased with the accumulation of toxicants in grass carp.4.Long-term exposure to BDE-209 could induce significant increase of CYP1 A and CYP3 A gene expression in a dose-effect relationship,which indicated that CYP1 A was sensitive to BDE-209.CYP1 A could be used as a biomarker of toxicological effects of BDE-209 on grass carp,and CYP3 A could be used as a biomarker of long-term exposure to BDE-209.5.In short-term exposure,BDE-209 could induce a significant increase in the expression of ERα,but the expression of ERα had no significant change compared with the control group at 31 days.This indicated that ERα could be used as a biomarker in short-term exposure to BDE-209,while high concentration of BDE-209 could inhibit the expression of ERβ1 in short-term exposure,while low concentration of BDE-209 could induce the expression of ERβ1,it’s specific mechanism needs further study.