Enrichment And Distribution Of 3,6-dichlorocarbazole In Carassius Auratus And Its Hepatotoxicity

Polyhalogenated carbazoles(PHCs)are a class of organic halogen compounds in which the hydrogen atom on the carbazole ring is replaced by halogen atom.They have a complex chemical structure similar to polychlorinated dibenzofurans.The preliminary study of toxicology experiment shows that PHCs have persistence,dioxin like toxicity and bioaccumulation.Carbazole and its derivatives are important nitrogen-containing aromatic heterocyclic compounds with a wide range of sources,such as the petroleum industry and the manufacture of carbazole based industrial materials,including dyes,drugs and pesticides,and are widely used in the fields of photoelectric materials,dyes,medicine and supramolecular recognition.In recent years,PHCs have been detected in various environments,such as sediment,soil,atmospheric particles and water.PHCs have been detected in more and more environmental samples,and their wide distribution in the environment and potential ecological harm have attracted more and more attention.However,at present,there are few studies on halocarbazole,and the research on the comprehensive toxic effects of PHCs at the biological individual level is even less.Therefore,in this study,3,6-dichlorocarbazole(3,6-DCCZ)was selected as the research object,and the carassius auratus was exposed in a semi-static way to determine the enrichment and purification of various tissues and organs of carassius auratus According to the concentration of 3,6-DCCZ accumulated and stabilized in carassius auratus,the enrichment coefficient of 3,6-DCCZ in various organs and tissues of carassius auratus was calculated.According to the results of enrichment experiment,the exposure experiment was carried out again.The carassius auratus was collected and the liver was dissected for toxicological study and histopathological observation.The main conclusions are as follows:(1)After exposure to 20 ?g/L for 20 days,the enrichment concentration of 3,6-DCCZ in various organs and tissues was as follows: brain > liver > intestine > gill > muscle;After exposure to 100 ?g/L for 20 days,the enrichment concentration of 3,6-DCCZ in various organs and tissues was as follows: brain > liver > gill > intestine > muscle.The purification experiment showed that 3,6-DCCZ would not accumulate in various organs and tissues of fish for a long time.(2)In general,both exposure concentrations will produce oxidative stress on carassius auratus.Among them,the increase of ROS content in the liver of carassius auratus in the 100?g/L treatment group was higher than that in the 20 ?g/L treatment group.After 5 days of exposure,the activation of SOD and GST in the liver of carassius auratus in the treatment group of 20 ?g/L was the highest,while the activation of CAT in the liver of carassius auratus in the treatment group of 100 ?g/L was the highest.After 20 days of exposure,the activation of SOD,CAT and GST in liver of carassius auratus in 100 ?g/L treatment group was the highest.(3)Both exposure concentrations could cause lipid peroxidation and DNA damage to the liver of carassius auratus.On the 5th day,the increase of MDA content in liver of 100 ?g/L treatment group was higher than that of 20 ?g/L treatment group.On the 20 th day,the degree of lipid peroxidation and DNA damage produced by the liver of carassius auratus in the 20 ?g/L treatment group were the highest.It may be that the activities of SOD and CAT in the 100 ?g/L treatment group were higher than those in the 20 ?g/L treatment group on the 20 th day,so as to reduce the oxidative damage to the liver.(4)Both exposure concentrations caused certain histopathological changes in the liver of crucian carp.In the 20 ?g/L treatment group,there was obvious cell gap increase and cell cavitation on the 5th day of exposure,and the cell cavitation and cell gap increase were more serious on the 20 th day,and there was nucleus pyknosis,indicating that low concentration 3,6-DCCZ exposure will cause certain damage to the liver of carassius auratus.In the 100 ?g/L treatment group,cell vacuolization,nucleus pyknosis and nucleus pleomorphism appeared on the 5th day of exposure,and even some no nucleus areas appeared on the 20 th day.The cell gap increased significantly with fat accumulation,indicating that high concentration 3,6-DCCZ exposure will cause more serious damage to the liver of carassius auratus and abnormal lipid metabolism.