Lin Y P, Upton P B, Sangaiah R, Swenberg J A
Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill 27599-7400, USA.
Toxicology. 1996 Oct 28;113(1-3):70-6. doi: 10.1016/0300-483x(96)03429-4.
Butadiene (BD) is an important industrial chemical classified as a probable human carcinogen. Marked species differences in susceptibility to the carcinogenic effects of BD have been observed, possibly due to the differences in its metabolism. In this work, guanine and adenine adducts formed by the reactive metabolites of BD in vitro were isolated and structurally characterized by UV spectroscopy, liquid secondary ion mass spectrometry and tandem mass spectrometry, electrospray mass spectrometry and nuclear magnetic resonance spectroscopy. The adducts were prepared by reacting purine nucleobases or nucleosides with epoxybutene (EB) or diepoxybutane (DEB) followed by HPLC separation. The reaction of guanine (Gua) with EB resulted in two isomeric products, N7-(2-hydroxy-3-buten-1-yl)guanine (EB-Gua I) and N7-(1-hydroxy-3-buten-2-yl)guanine (EB-Gua II). The reaction of adenine at N3 led to the formation of N3-(2-hydroxy-3-buten-1-yl)adenine (EB-Ade I) and N3-(1-hydroxy-3-buten-2-yl) (EB-Ade II). The major guanine adduct with DEB was identified as N7-(2',3', 4'-trihydroxybutyl)guanine (DEB-Gua-I). Three products formed from the reaction of DEB with adenine at pH 7 were identified as N3, N7 and N9-(2',3',4'-trihydroxybutyl)adenines (DEB-Ade I, II and III, respectively). Our results indicate that nucleophilic nitrogens of guanine and adenine first attack one of the epoxy groups of DEB giving (2'-hydroxy-3',4'-epoxybutane-1-yl) intermediates which can be rapidly hydrolyzed to the corresponding (2',3',4'-trihydroxybutyl) adducts or form cross-links with DNA or proteins. N7 and N3 adducts of Ade and Gua are expected to undergo spontaneous depurination and repair by methylpurine glycosylase and therefore may be useful as biomarkers of exposure in urine. The preliminary data on quantification of EB-induced N-terminal valine hemoglobin adducts in red blood cells of exposed mice and rats using modified Edman degradation followed by GC-NI MS was investigated. The amount of EB-N-terminal valine adducts in mouse globin was about 3 times greater than that in rats which may be explained by higher rates of the formation and/or limited detoxification of EB in mice. Female rats and mice had greater amounts of hemoglobin adducts than males.
丁二烯（BD）是一种重要的工业化学品，被归类为可能的人类致癌物。已观察到不同物种对BD致癌作用的易感性存在显著差异，这可能是由于其代谢差异所致。在本研究中，通过紫外光谱、液体二次离子质谱和串联质谱、电喷雾质谱以及核磁共振光谱，对BD体外反应性代谢产物形成的鸟嘌呤和腺嘌呤加合物进行了分离和结构表征。加合物通过嘌呤碱基或核苷与环氧丁烯（EB）或1,2 - 二环氧丁烷（DEB）反应，随后进行高效液相色谱分离制备。鸟嘌呤（Gua）与EB反应产生两种异构体产物，N7 - （2 - 羟基 - 3 - 丁烯 - 1 - 基）鸟嘌呤（EB - Gua I）和N7 - （1 - 羟基 - 3 - 丁烯 - 2 - 基）鸟嘌呤（EB - Gua II）。腺嘌呤在N3位的反应导致形成N3 - （2 - 羟基 - 3 - 丁烯 - 1 - 基）腺嘌呤（EB - Ade I）和N3 - （1 - 羟基 - 3 - 丁烯 - 2 - 基）腺嘌呤（EB - Ade II）。与DEB形成的主要鸟嘌呤加合物被鉴定为N7 - （2',3',4' - 三羟基丁基）鸟嘌呤（DEB - Gua - I）。在pH 7条件下，DEB与腺嘌呤反应形成的三种产物分别被鉴定为N3、N7和N9 - （2',3',4' - 三羟基丁基）腺嘌呤（分别为DEB - Ade I、II和III）。我们的结果表明，鸟嘌呤和腺嘌呤的亲核氮原子首先攻击DEB的一个环氧基团，生成（2' - 羟基 - 3',4' - 环氧丁烷 - 1 - 基）中间体，该中间体可迅速水解为相应的（2',3',4' - 三羟基丁基）加合物，或与DNA或蛋白质形成交联。预计腺嘌呤和鸟嘌呤的N7和N3加合物会发生自发脱嘌呤，并由甲基嘌呤糖基化酶进行修复，因此可能作为尿液中暴露的生物标志物。研究了使用改良的埃德曼降解法继而进行气相色谱 - 负离子质谱法对暴露小鼠和大鼠红细胞中EB诱导的N - 末端缬氨酸血红蛋白加合物进行定量的初步数据。小鼠珠蛋白中EB - N - 末端缬氨酸加合物的量约为大鼠的3倍，这可能是由于小鼠中EB形成速率较高和/或解毒有限所致。雌性大鼠和小鼠的血红蛋白加合物含量高于雄性。
