Biological Evaluation of the Environmental Pollution Based on the Induction of ECOD Activity in Human Hepatoma HepG2 Cells

在基于芳烃受体（AhR）依赖性诱导HepG 2细胞中7-乙氧基香豆素O-脱乙基酶（ECOD）活性的测定系统中，使用河流沉积物提取物，比较研究了流入东京湾的河流和流入相模湾的相模河的污染程度。位于京滨工业区中部的鹤见河被认为污染最严重。在鹤见河Namamugi采样的严重污染的河流沉积物的提取物显示出一个倒U形的剂量-反应曲线，多环芳烃（PAHs）可能是主要负责，在无毒浓度范围内。Namamugi样本的污染粗略估计为2至20微克多环芳烃/克土壤。通过对鹤见江污染的纵向研究发现，位于中游的原露天工业垃圾焚烧场不是造成鹤见江河口重污染的原因，河流沉积物提取物和3-甲基胆蒽（3-MC）的ECOD活性呈倒U型剂量-反应曲线，反映在CYP 1A蛋白的剂量-反应曲线中，而HepG 2细胞中CYP 1A 1 mRNA的表达在较高浓度下基本保持稳定，这意味着在较高的AhR激动剂水平下翻译受到抑制。

The extents of pollution of the rivers flowing into Tokyo Bay as well as the Sagami River draining into Sagami Bay were studied comparatively using river sediment extracts in an assay system based on the aryl hydrocarbon receptor (AhR)-dependent induction of 7-ethoxycoumarin O-deethylase (ECOD) activity in HepG2 cells. The Tsurumi River located in the middle of Keihin Industrial District was considered most polluted. The extract of heavily polluted river sediments sampled at Namamugi on the Tsurumi River showed a reverse U-shaped dose-response curve, for which polycyclic aromatic hydrocarbons (PAHs) might be mainly responsible, in a range of non-toxic concentrations. The pollution of the Namamugi sample was roughly estimated to be 2 to 20 μg as PAHs/g soil. Based on the longitudinal study on the pollution of the Tsurumi River, the former open-air industrial waste incineration site located in the midstream was found not to be a cause for the heavy pollution at the river mouth.The reverse U-shaped dose-response curve in terms of ECOD activity shown by the river sediment extracts as well as 3-methylcholanthrene (3-MC) was reflected in the dose-response curve for the CYP1A protein, whereas the expression of CYP1A1 mRNA in HepG2 cells remained roughly stationary at higher concentrations, implying translational suppression at higher AhR agonist levels.The XRE-luciferase gene reporter assay based on the transient transfection was found to be superior to the ECOD assay, in which time-wasting deglycosylation step was unavoidable, with respects to quantitativeness and reliability.