Guichard Y, el Ghissassi F, Nair J, Bartsch H, Barbin A
International Agency for Research on Cancer, Lyon, France.
Carcinogenesis. 1996 Aug;17(8):1553-9. doi: 10.1093/carcin/17.8.1553.
DNA ethenobases are promutagenic lesions formed by carcinogens such as vinyl chloride (VC). Their formation was investigated in 6-week old, male Sprague-Dawley rats exposed to 500 p.p.m. VC by inhalation (4 h/day, 5 days/ week) for 1, 2, 4 or 8 weeks and in 7- and 14-week old, matched control animals. 1,N6-Ethenoadenine (epsilon A) and 3, N4-ethenocytosine (epsilon C) deoxyribonucleotides were analysed by immunoaffinity purification and 32P-postlabelling. This postlabelling method was compared with a radio-immunoassay method, which yielded similar results. Background levels of ethenobases were found in DNA from the liver, lungs, kidneys and circulating lymphocytes of unexposed, control rats. In the liver, the following background molar ratios of ethenobase to parent base in DNA were detected (mean values x 10(-8)): epsilon A/A, 0.04-0.05; epsilon C/C, 0.06-0.07. In the lungs, kidneys and circulating lymphocytes, background levels of epsilon A and epsilon C ranged from 1.7 to 4.2 x 10(-8) and from 4.8 to 11.2 x 10(-8), respectively. Following a 5-day exposure to VC, a significant increase of epsilon A and epsilon C was measured in hepatic DNA from rats sacrificed immediately after treatment. Further, a dose-dependent increase of both etheno adducts was observed in liver DNA of VC-treated rats. Compared to the 5-day exposure, approximately 4-fold higher levels of epsilon A and epsilon C were observed in the liver of animals after 8 weeks of exposure. In contrast, there was an accumulation of epsilon C but not of epsilon A in lungs and kidneys. In circulating lymphocytes, no significant increase of ethenobase levels above control values was observed after 2 months of exposure to VC. Both etheno adducts were found to be persistent in liver DNA, after 2 months following the termination of VC exposure. These results further support the notion that DNA etheno-bases are critical lesions in VC-induced carcinogenesis. The possible contribution of lipid peroxidation products that also yield ethenobases, on the formation and persistence of these DNA adducts, remains to be clarified.
DNA 乙烯基化碱基是由氯乙烯（VC）等致癌物形成的促诱变损伤。在6周龄雄性Sprague-Dawley大鼠中研究了它们的形成情况，这些大鼠通过吸入500 ppm的VC（每天4小时，每周5天）暴露1、2、4或8周，并与7周龄和14周龄的匹配对照动物进行比较。通过免疫亲和纯化和32P后标记分析1,N6-乙烯基腺嘌呤（εA）和3,N4-乙烯基胞嘧啶（εC）脱氧核糖核苷酸。将这种后标记方法与放射免疫分析法进行比较，结果相似。在未暴露的对照大鼠的肝脏、肺、肾脏和循环淋巴细胞的DNA中发现了乙烯基化碱基的背景水平。在肝脏中，检测到DNA中乙烯基化碱基与亲本碱基的以下背景摩尔比（平均值×10^(-8)）：εA/A，0.04 - 0.05；εC/C，0.06 - 0.07。在肺、肾脏和循环淋巴细胞中，εA和εC的背景水平分别为1.7至4.2×10^(-8)和4.8至11.2×10^(-8)。在暴露于VC 5天后，对处理后立即处死的大鼠肝脏DNA中εA和εC的含量进行了显著增加的测量。此外，在VC处理的大鼠肝脏DNA中观察到两种乙烯基加合物均呈剂量依赖性增加。与5天暴露相比，暴露8周后动物肝脏中εA和εC的水平高出约4倍。相比之下，肺和肾脏中εC有积累而εA没有。在循环淋巴细胞中，暴露于VC 2个月后未观察到乙烯基化碱基水平比对照值有显著增加。在VC暴露终止2个月后，两种乙烯基加合物在肝脏DNA中均持续存在。这些结果进一步支持了DNA乙烯基化碱基是VC诱导致癌作用中的关键损伤这一观点。脂质过氧化产物也会产生乙烯基化碱基，其对这些DNA加合物形成和持续存在的可能贡献仍有待阐明。
