Migration,Biotransformation And Maternal Transfer Of Indicator Polychlorinated Biphenyls (IN-PCBs) In Laying Hens

Polychlorinated biphenyls(PCBs)and their hydroxylated metabolites(OH-PCBs)were ubiquitously found in the environment as well as in several kinds of foodstuffs,leading to a great threat to human and animal health.However,limited information is available on the migration and biotransformation of PCBs in domestic animals.To fill this knowledge gap,the following studies were carried out on seven indicator PCBs(IN-PCBs)whose concentrations in the environment were relatively higher than the other PCBs.High sensitive determination methods of IN-PCBs and OH-PCBs in animal origin samples using gas chromatography-tandem mass spectrometry(GC-MS/MS)were established.The fat removing procedure using sulfuric acid silica gel was optimized,the adsorption-desorption behavior of IN-PCBs on silica gel column was studied,and an automatic pressurizing device with glass clean-up column was developed,to accomplish the high-throughput,high efficiency,and low organic solvent consumption purposes of the sample pre-treatment.We proposed a new idea on the clean-up methods of OH-PCBs based on “reverse extraction-freeze centrifugation-sulfuric acid silica gel”,which simplified the OH-PCBs sample pre-treatment procedures and extended the range of target OH-PCBs.In vitro metabolism of IN-PCBs using chicken liver microsomes was performed.The capability of PCBs metabolism highly depended on the position of chlorination in PCBs molecular.The PCB congeners with adjacent non-chlorine substituted carbon atoms in the para-and meta-positions(PCB52 and PCB 101)were readily biotransformed into OH-PCBs.On the contrary,the majority of IN-PCBs with bi-para-chlorine substituted carbon atoms(PCB 28,PCB 118,PCB 138,PCB 153,and PCB 180)were fairly resistant towards hydroxylated metabolism reaction.The Km of PCB 101 hydroxylated metabolism with chicken liver microsomes was about 5.7 ?mol/L,and the Vmax of 4`-OH-PCB 101 was4 times bigger than that of 3`-OH-PCB101.The fate of IN-PCBs in laying hens with the consumption of contaminated feed was investigated.Generally,IN-PCBs had the characteristics of high absorption rate,high lipophilicity and high intergenerational transfer in laying hens.The fate of IN-PCBs in laying hens highly depended on the number and the position of chlorine atoms in PCBs.The chlorine substituted position was involved in the metabolism,and the number of chlorine determined the IN-PCBs bioaccumulation behavior through the “feed-laying hen-egg-chick” chain.IN-PCBs with a higher degree of chlorination were less bioavailable and more bioaccumulative in eggs than lower chlorinated congeners.The pattern of4`-OH-PCB 101 in hens was significantly different from their precursors.The OH-PCB werasmore easily remained in the blood and transferred into eggs,but difficult to be accumulated in the fat tissue.Among them,the concentration of 4'-OH-PCB 101 in plasma was 3.7,23.8 and 200 times higher than those in the yolk,liver and fat,respectively.The maternal transfer of IN-PCBs and 4`-OH-PCB 101 from laying hen to chick was studied.The concentration and relative abundance of IN-PCBs in tissues of newborn chicks were different from that in maternal hens.The total concentrations of IN-PCBs in chick liver and muscle were higher than those in hens,respectively.For the individual congeners,the IN-PCBs with more chlorines had a higher content in chick tissues.Chick embryos might have the capability of metabolizing the PCBs,resulting in higher ratio of 4`-OH-PCB 101/PCB 101 compared with that in hens.In conclusion,the results of the present study can provide reliable technological methods for IN-PCBs and OH-PCBs detection and unknown OH-PCBs identification,and fundamental basis for PCBs risk assessment and source analysis on laying hens.