Fernando R C, Nair J, Barbin A, Miller J A, Bartsch H
German Cancer Research Center, Division of Toxicology and Cancer Risk Factors, Heidelberg, Germany.
Carcinogenesis. 1996 Aug;17(8):1711-8. doi: 10.1093/carcin/17.8.1711.
The capacity of the chemical carcinogen ethyl carbamate (EC, urethane) and its metabolites vinyl carbamate (VC) and vinyl carbamate epoxide (VCO) to form ethenobases was studied in liver and lung DNA of 12-day-old and adult CD-1, B6C3F1, C3H/HeJ and C57BL/6J mice. Following single and multiple doses of EC, VC or VCO, the formation of 1,N6-ethenodeoxyadenosine (epsilon dA) and 3,N4-ethenodeoxycytidine (epsilon dC) was quantified by an immunoaffinity chromatography/32P-postlabelling technique. Both etheno adducts were detected in untreated control DNA samples from liver and lung in the range of 2-15 adducts/10(9) parent nucleotides. Following five repeated injections of 250 or 280 nmol/g body wt VC to adult mice, 51, 57 and 78 epsilon dA/10(9) dA and 28, 42 and 42 epsilon dC/10(9) dC (means of duplicate analyses) were detected in liver DNA of CD-1, C3H/HeJ and C57BL/6J mice respectively. In lung DNA of these VC-treated mice, the levels were 87, 49 and 58 (epsilon dA/10(9) dA) and 64, 39 and 43 (epsilon dC/10(9) dC) respectively. Under similar dose regimens, lower levels of etheno adducts were detected in B6C3F1 mice. Etheno-DNA adducts were also formed in liver and lung upon treatment with EC in adult mice, but at 3-fold lower levels as compared with VC. In 12-day-old C3H/HeJ and C57BL/6J mice, 2- to 3-fold higher etheno adduct levels were detected in liver DNA, when compared with adults, upon a single treatment with 250 nmol/g body wt VC, suggesting that young animals are more susceptible to adduct formation. Combined analysis of adduct formation in adult CD-1, C3H/HeJ and C57BL/6J mice at the higher dose showed a statistically significant increase in etheno adduct formation in the order EC > VC. The results demonstrate that EC and its activated intermediates bind to liver and lung DNA to form epsilon dA and epsilon dC, and the differences in DNA binding further support the hypothesis that metabolic activation of EC to VC is involved. Preliminary data also suggest that background levels of epsilon dA and epsilon dC in DNA are affected by the type of diet given to the animals.
研究了化学致癌物氨基甲酸乙酯（EC，urethane）及其代谢产物氨基甲酸乙烯酯（VC）和氨基甲酸乙烯酯环氧化物（VCO）在12日龄和成年CD-1、B6C3F1、C3H/HeJ和C57BL/6J小鼠肝脏和肺脏DNA中形成乙烯基碱基的能力。给予单次和多次剂量的EC、VC或VCO后，通过免疫亲和色谱/32P后标记技术对1,N6-乙烯基脱氧腺苷（εdA）和3,N4-乙烯基脱氧胞苷（εdC）的形成进行定量。在肝脏和肺脏未处理的对照DNA样品中检测到两种乙烯基加合物，其含量范围为2 - 15个加合物/10^9个亲本核苷酸。对成年小鼠重复注射5次250或280 nmol/g体重的VC后，在CD-1、C3H/HeJ和C57BL/6J小鼠肝脏DNA中分别检测到51、57和78个εdA/10^9个dA以及28、42和42个εdC/10^9个dC（重复分析的平均值）。在这些经VC处理的小鼠肺脏DNA中，含量分别为87、49和58（εdA/10^9个dA）以及64、39和43（εdC/10^9个dC）。在相似的剂量方案下，B6C3F1小鼠中检测到的乙烯基加合物水平较低。成年小鼠经EC处理后，肝脏和肺脏中也形成了乙烯基-DNA加合物，但与VC相比，水平低3倍。在12日龄的C3H/HeJ和C57BL/6J小鼠中，单次给予250 nmol/g体重的VC后，与成年小鼠相比，肝脏DNA中检测到的乙烯基加合物水平高2至3倍，这表明幼龄动物更容易形成加合物。对成年CD-1、C3H/HeJ和C57BL/6J小鼠在高剂量下加合物形成的综合分析表明，乙烯基加合物形成的增加在统计学上具有显著差异，顺序为EC > VC。结果表明，EC及其活化中间体与肝脏和肺脏DNA结合形成εdA和εdC，DNA结合的差异进一步支持了EC代谢活化为VC的假说。初步数据还表明，DNA中εdA和εdC的背景水平受给予动物的饮食类型影响。
