GENETIC TOXICITY IN BACTERIA AND RODENTS

遗传毒性测试合同规定评估接触NTP正在研究的化合物的潜在不利遗传影响。采用的检测系统包括体外(基于动物细胞和细菌)和体内(大鼠和小鼠)检测。常规进行三项主要试验：体外细菌致突变试验、体内鼠外周血微核(MN)试验和体内多组织DNA损伤(彗星试验)试验。现在，MN检测通常通过对准备好的血液样本进行流式细胞仪分析来收集数据，而不是通过记分玻片。这一创新提供了更强的检测诱发染色体损伤的能力，并提高了测试的客观性以及数据收集的速度。MN和彗星检测通常使用同一组动物进行，从而最大限度地从单一处理的动物中收集数据，减少动物使用，并降低成本。在上个财政年度，启动或完成了38项微生物诱变性检测和17项体内微核检测。已经在一个或多个组织中进行了16次体内彗星试验，包括血液、肝脏、肾脏、胃、结肠和脑。此外，还与NIEHS的一个实验室合作进行了彗星试验，以比较几个不同细胞系之间的DNA修复活动，以努力更好地了解与特定癌症相关的某些突变基因的作用。一项旨在检测低剂量苯暴露对遗传多样性小鼠的影响的NTP研究已经启动，最终可能有助于为工人建立较低的暴露限值；苯暴露小鼠血液和骨髓中的微核率将是这项NTP研究评估的主要生物标志物。在过去的这一财年中，另一个有望在未来应用于人类临床和生物监测研究的动物突变终点在测试实验室进行了检测：PIG-A突变试验(磷脂酰肌醇葡聚糖锚定生物合成，A类基因)。在实验室啮齿动物的红细胞样本中很容易检测到这种基因的突变，并且已经成功地在老鼠身上进行了验证研究。在下一财年，我们将尝试将这种检测与体内MN和彗星检测相结合，增加我们从实验动物那里获得的遗传毒性信息，以提供一种化学物质遗传毒性潜力的更全面的概况。

The Genetic Toxicity Testing contract provides for the assessment of potential adverse genetic effects from exposure to compounds under study by the NTP. Testing systems employed include both in vitro (animal cell-based and bacterial) and in vivo (rats and mice) assays. Three main tests are conducted routinely: in vitro bacterial mutagenicity assays, in vivo rodent peripheral blood micronucleus (MN) assays, and in vivo rodent DNA damage (Comet) assays in multiple tissues. The MN assays now routinely collect data by flow cytometric analysis of prepared blood samples rather than by scoring slides. This innovation has provided greater ability to detect induced chromosomal damage and has improved the objectivity of the test, as well as the speed of data collection. MN and Comet assays are typically conducted with the same set of animals, thereby maximizing data collection from a single treated animal, reducing animal usage, and reducing costs. During the past fiscal year, 38 microbial mutagenicity assays and 17 in vivo micronucleus assays have been initiated or completed. Sixteen in vivo Comet assays have been conducted in one or multiple tissues including blood, liver, kidney, stomach, colon, and brain. In addition, Comet assays have been conducted in vitro, in collaboration with an NIEHS laboratory, to compare DNA repair activities among several different cell lines in an effort to better understand the role of certain mutant genes associated with particular cancers. An NTP research study designed to examine the effects of low dose benzene exposure in genetically diverse mice has been initiated that may ultimately help to establish lower exposure limits for workers; micronucleus frequencies in blood and bone marrow of benzene-exposed mice will be a major biomarker assessed in this NTP study. During this past fiscal year, another animal mutation endpoint that holds promise for application in human clinical and biomonitoring studies in the future, has been examined in the testing laboratory: the pig-a mutation assay (phosphatidylinositol glycan anchor biosynthesis, class A gene). Mutations in this gene are easily detected in red blood cell samples from laboratory rodents and validation studies in mice have been successfully conducted. During the next fiscal year, we will attempt to multiplex this assay with the in vivo MN and Comet assays, increasing the genetic toxicity information that we obtain from test animals to provide an even more comprehensive profile of the genetic toxicity potential of a chemical.