| Benzo（a）pyrene,as a highly persistent organic pollutant,is widely distributed in the environment and enters into the water environment with rainfall,industrial wastewater and oil spill from ships,so that benzo（a）pyrene pollution is getting worse,causing widespread concern.We selected Cyprinus carpio,a freshwater economic species,to study the acute toxic effects of benzo（a）pyrene on common carp under laboratory conditions,The effects of benzo（a）pyrene on major biomarkers in common carp at different exposure time（2 d,6 d,10 d）and the effect of long-term exposure on the microstructure of carp liver,gill and gonadal tissues,effect of structure.The following results can be drawn:1.The results of acute toxicity test showed that the 96 h LC500 of benzo（a）pyrene against carp was2.591 mg/L under water exposure.According to the classification standard of acute toxicity of fish,benzo（a）pyrene is a highly toxic substance for carp.2.The main biomarkers in common carp showed that the activities of SOD and POD in the common carp exposed to benzo（a）pyrene were"low and high",which indicated that carp was exposed to low level of external stress（50μg/L,100μg/L）,but when the concentration of benzo（a）pyrene exceeds a certain range,the activity of SOD and POD decreased significantly,which was significantly lower than that of the control group,which caused oxidative damage to carp.With the increase of benzo（a）pyrene concentration,MDA content increased significantly,indicating that part of the carp tissue lipid peroxidation,resulting in membrane damage;The responses of SOD,POD,and MDA in different tissues were significantly different.The liver,sputum,kidney,heart,and other tissues responded more than gonads,brain,and muscle.In addition,detoxification and metabolism of enzymes GST,AHH,EROD activity increased,indicating that it may be Metabolic damage occurs.3.The paraffin section microscopic analysis showed that after exposure to benzo（a）pyrene for 15days,the tissues and organs of the squid appeared different large numbers and some of the cavities appear.The cavities appear partly;Shrinkage,nuclear dissolution and cytoplasmic vacuolization and other phenomena;the number of gonadal cells decreased,the cells become larger,the nucleus shrinkage,and even nuclear rupture,cell vacuolization.4.Transmission electron microscopy results showed that exposure to benzo（a）pyrene solution for24 days,will cause damage to the structure of carp liver cells,and with the increase in the concentration of benzo（a）pyrene,the degree of damage is intensified.Low concentrations of benzo（a）pyrene will cause carp liver cell nucleus deformation,shrinkage,mitochondrial deformation,distortion,endoplasmic reticulum rupture,fragmentation,vesicular,some hepatocytes vacuolar.High concentration of benzo（a）pyrene can cause carp liver cell nucleus lysis,organelles less,and more severely damaged lipid droplets increased vacuolization worse. |
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