Yamaguchi R, Hirano T, Asami S, Chung M H, Sugita A, Kasai H
Department of Environmental Oncology, University of Occupational and Environmental Health, Kitakyushu, Japan.
Carcinogenesis. 1996 Nov;17(11):2419-22. doi: 10.1093/carcin/17.11.2419.
The renal carcinogen, ferric nitrilotriacetate (Fe-NTA), is known to induce oxidative stress and the subsequent formation of a type of oxidative DNA damage, 8-hydroxyguanine (8-OH-Gua), in the rat kidney (Umemura et al., 1990). Using an improved DNA isolation method (Nakae et al., 1995), which reduces the background level of 8-OH-Gua, we found a five-fold increase in the 8-OH-Gua level in kidney DNA after a single i.p. injection of Fe-NTA. On the basis of the report that 8-OH-Gua repair activity is enhanced after cells are exposed to oxidative stress due to ionizing radiation (Bases et al., 1992), the measurement of 8-OH-Gua repair activity will also be useful to assess cellular oxidative stress. The 8-OH-Gua repair enzyme activity was determined with an endonuclease assay using a 22 mer DNA that contains 8-OH-Gua at a specific position. A five-fold increase in the 8-OH-Gua repair activity as compared with the control, was observed in the target organ, the rat kidney, 120 h after Fe-NTA administration. In the non-target organ, the liver, the increase was not as large (two-fold). This simple assay of oxidative DNA damage repair will be useful for evaluating the carcinogenicity of oxygen radical forming chemicals, in addition to chemical analyses of oxidative DNA damage.
已知肾致癌物次氮基三乙酸铁（Fe-NTA）可在大鼠肾脏中诱导氧化应激，并随后形成一种氧化性DNA损伤，即8-羟基鸟嘌呤（8-OH-Gua）（Umemura等人，1990年）。使用一种改进的DNA分离方法（Nakae等人，1995年），该方法可降低8-OH-Gua的背景水平，我们发现腹腔单次注射Fe-NTA后，肾脏DNA中的8-OH-Gua水平增加了五倍。基于细胞在受到电离辐射引起的氧化应激后8-OH-Gua修复活性增强的报告（Bases等人，1992年），测量8-OH-Gua修复活性对于评估细胞氧化应激也将是有用的。使用在特定位置含有8-OH-Gua的22聚体DNA通过核酸内切酶测定法测定8-OH-Gua修复酶活性。在给予Fe-NTA 120小时后，在靶器官大鼠肾脏中观察到8-OH-Gua修复活性与对照相比增加了五倍。在非靶器官肝脏中，增加幅度没有那么大（两倍）。这种简单的氧化性DNA损伤修复测定法除了用于氧化性DNA损伤的化学分析外，还将有助于评估形成氧自由基的化学物质的致癌性。
