NITROSAMINE ACTIVATION AND EXTRAHEPATIC P450S

描述：亚硝胺对动物有很强的致癌性， 对人类也有致癌作用。 在大鼠中，食管是 对亚硝胺诱发肿瘤最敏感的器官。 的 亚硝胺的肿瘤诱导特异性被认为是由于 组织特异性激活（α-羟基化）的P-450酶定位在 食管，如NNN和NBzMA的有效激活所示 （分别为N '-亚硝基去甲烟碱和N-亚硝基苄基甲胺）。 的 本项目的目标是分离和表征P450酶， 对亚硝胺活化有特异性的大鼠食管。 初步 对人P450、大鼠鼻粘膜和大鼠食管微粒体的研究， 表明P450 2A酶在激活 亚硝胺 这个项目的工作假设是， 大鼠食管和鼻组织中的激活是由于2A的P450 家人 从大鼠食管和鼻粘膜组织中构建cDNA文库， 产生，并且将用一个或多个P450 2A基因筛选文库 片段 将得到的cDNA测序并在大肠杆菌中表达。 昆虫细胞的杆状病毒表达系统。 表达的P450 将检测NNN和NBzMA羟基化活性。 使用这些P450 和各种相关的亚硝胺，假设将被测试， 亚硝胺是强食管致癌物， 已经分离出的组织特异性P450。 根据该 假设，降低致癌性的结构变化， 也会导致P450介导的激活减少。 最后，人类 将对食管进行分析，以确定是否存在类似的P450酶特异性 亚硝胺的活化作用。

DESCRIPTION: Nitrosamines are strongly carcinogenic in animals and are believed to be carcinogenic in humans as well. In rats, the esophagus is the most susceptible organ to tumor induction by nitrosamines. The specificity of tumor induction of nitrosamines is believed to be due to tissue-specific activation (a-hydroxylation) by P-450 enzymes localized in the esophagus, as shown by the efficient activation of both NNN and NBzMA (N'-Nitrosonornicotine and N-Nitrosobenzylmethylamine, respectively). The goal of this project is to isolate and characterize the P450 enzyme(s) in rat esophagus that are specific for nitrosamine activation. Preliminary studies with human P450s, rat nasal mucosa and rat esophageal microsomes, indicate that P450 2A enzymes play an important role in the activation of nitrosamines. The working hypothesis in this project is that nitrosamine activation in rat esophagus and nasal tissue is due to P450s of the 2A family. A cDNA library from rat esophagus and nasal mucosa tissue will be generated, and the library will be screened with one or more P450 2A gene fragments. The resulting cDNAs will be sequenced and will be expressed in insect cells using the baculovirus expression system. The expressed P450s will be tested for NNN and NBzMA hydroxylation activity. Using these P450s and various related nitrosamines, the hypothesis will be tested that nitrosamines which are strong esophageal carcinogens are good substrates for the tissue specific P450s that have been isolated. According to this hypothesis, a change in the structure which decreases the carcinogenicity, will also result in a decreased P450-mediated activation. Finally, human esophagus will be analyzed to determine if a similar P450 enzyme specific for nitrosamine activation is present.