Gould J C, Cooper K R, Scanes C G
Joint Graduate Program in Toxicology, Rutgers, The State University of New Jersey and the University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08855, USA.
Ecotoxicol Environ Saf. 1999 Jun;43(2):195-203. doi: 10.1006/eesa.1999.1776.
Polychlorinated biphenyls (PCBs) are widespread environmental contaminants which can biomagnify to higher tropic level organisms including birds. Circulating thyroid hormones (TH) and growth are decreased by PCB exposure. The first set of studies investigated the effects of PCBs on an enzyme responsible for TH homeostasis, hepatic type I monodeiodinase (MDI) in chicken embryos. Fertile chicken eggs were injected with Aroclor 1242, Aroclor 1254, 2,2',6, 6'-tetrachlorobiphenyl (TCB), 3,3',4,4'-TCB, or 3,3',5,5'-TCB on Day 0 and studies were terminated on Incubation Day 21. Hepatic MDI activity was reduced in embryos treated with the Aroclor mixtures. No effects on MDI activities were observed after PCB isomer treatment. Liver weights from embryos treated with Aroclor 1242 were decreased. In the second study, chick embryos were exposed to these same PCBs in order to evaluate their effect on circulating THs and growth. Treatment with PCBs had no effect on body weight. Femur length were decreased with Arcolor 1242 treatment. A decrease in plasma concentration of thyroxine was observed after treatment with Aroclor 1242 and Aroclor 1254. Based on these findings, it is evident that PCBs alter the thyroid axis. Bird circulating TH levels, which are generally reported, may not be a good biomarker for low-dose exposure to PCBs. However, the reduction in MDI activity was more sensitive to PCB mixture exposure and may be a useful biomarker.
多氯联苯（PCBs）是广泛存在的环境污染物，可在包括鸟类在内的更高营养级生物体内生物放大。PCB暴露会降低循环甲状腺激素（TH）水平并影响生长。首批研究调查了PCBs对鸡胚中负责TH稳态的一种酶——肝I型单脱碘酶（MDI）的影响。在第0天给受精鸡蛋注射Aroclor 1242、Aroclor 1254、2,2',6,6'-四氯联苯（TCB）、3,3',4,4'-TCB或3,3',5,5'-TCB，研究在孵化第21天结束。用Aroclor混合物处理的胚胎中肝MDI活性降低。PCB异构体处理后未观察到对MDI活性的影响。用Aroclor 1242处理的胚胎肝脏重量降低。在第二项研究中，鸡胚暴露于相同的PCBs以评估其对循环THs和生长的影响。PCBs处理对体重没有影响。用Arcolor 1242处理后股骨长度降低。用Aroclor 1242和Aroclor 1254处理后观察到甲状腺素血浆浓度降低。基于这些发现，很明显PCBs会改变甲状腺轴。通常报道的鸟类循环TH水平可能不是低剂量PCB暴露的良好生物标志物。然而，MDI活性的降低对PCB混合物暴露更敏感，可能是一种有用的生物标志物。
