(Table 1) Polychlorinated biphenyl (PCB) and PCB metabolite concentrations in ringed seals (Phoca hispida) from Svalbard and the Baltic Sea@en

Polychlorinated biphenyls (PCBs) may induce activity of hepatic enzymes, mainly Phase I monooxygenases and conjugating Phase II enzymes, that catalyze the metabolism of PCBs leading to formation of metabolites and to potential adverse health effects. The present study investigates the concentration and pattern of PCBs, the induction of hepatic phase I and II enzymes, and the formation of hydroxy (OH) and methylsulfonyl (CH3SO2=MeSO2) PCB metabolites in two ringed seal (Phoca hispida) populations, which are contrasted by the degree of contamination exposure, that is, highly contaminated Baltic Sea (n = 31) and less contaminated Svalbard (n = 21). Phase I enzymes were measured as ethoxyresorufin-O-deethylation (EROD), benzyloxyresorufin-O-dealkylation (BROD), methoxyresorufin-O-demethylation (MROD), and pentoxyresorufin-O-dealkylation (PROD) activities, and phase II enzymes were measured as uridine diphosphophate glucuronosyl transferase (UDPGT) and glutathione-S-transferase (GST). Geographical comparison, multivariate, and correlation analysis indicated that sum-PCB had a positive impact on Phase I enzyme and GST activities leading to biotransformation of group III (vicinal ortho-meta-H atoms and <=1 ortho-chlorine (Cl)) and IV PCBs (vicinal meta-para-H atoms and <=2 ortho-Cl). The potential precursors for the main OH-PCBs detected in plasma in the Baltic seals were group III PCBs. MeSO2-PCBs detected in liver were mainly products of group IV PCB metabolism. Both CYP1A- and CYP2B-like enzymes are suggested to be involved in the PCB biotransformation in ringed seals.多氯联苯（Polychlorinated biphenyls, PCBs）可诱导肝酶活性，主要包括I相单加氧酶（Phase I monooxygenases）与II相结合酶（Phase II enzymes），这类酶可催化多氯联苯的代谢过程，进而生成代谢产物并引发潜在的不良健康效应。本研究针对两种环斑海豹（Phoca hispida）种群，探究其体内多氯联苯的浓度与分布模式、肝I相及II相酶的诱导效应，以及羟基（OH）和甲基磺酰基（CH3SO2=MeSO2）多氯联苯代谢物的生成情况；这两个种群的污染物暴露程度存在显著差异，分别为污染程度较高的波罗的海种群（n=31）与污染程度较低的斯瓦尔巴群岛种群（n=21）。I相酶活性通过检测乙氧基试卤灵-O-脱乙基酶（EROD）、苄氧基试卤灵-O-脱烷基酶（BROD）、甲氧基试卤灵-O-脱甲基酶（MROD）以及戊氧基试卤灵-O-脱烷基酶（PROD）的活性进行表征；II相酶活性则通过检测尿苷二磷酸葡萄糖醛酸转移酶（UDPGT）与谷胱甘肽S-转移酶（GST）的活性进行表征。地理比较、多变量及相关性分析结果显示：总多氯联苯（sum-PCB）对I相酶及谷胱甘肽S-转移酶（GST）活性具有正向促进作用，进而介导第III类（邻位-间位氢原子邻接且≤1个邻位氯（Cl）取代）与第IV类（间位-对位氢原子邻接且≤2个邻位氯取代）多氯联苯的生物转化。波罗的海海豹血浆中检出的主要羟基多氯联苯（OH-PCBs）的潜在前体为第III类多氯联苯。肝脏中检出的甲基磺酰基多氯联苯（MeSO2-PCBs）主要源自第IV类多氯联苯的代谢产物。研究表明，CYP1A样酶（CYP1A-like）与CYP2B样酶（CYP2B-like）均参与了环斑海豹体内的多氯联苯生物转化过程。