Genetic Toxicity Testing Services for the NTP

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。这种方法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。在过去的一个财政年度中，启动或完成了大约11项微生物诱变性检测和9项体内微核检测。40个体内彗星试验已经在一个或多个组织中进行，包括血液、肝脏、肾脏、胃、结肠和脑。在下一财政年度，预计将进一步强调基因突变和染色体损伤的体外测量，以继续减少和改进我们对整个动物试验的使用。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研究：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，并开发了简化检测的最新方法，以便更好地整合到现有的毒性测试中。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。目前，计划进行2项PIG-a研究，并将MN研究纳入现有的NTP毒性研究。除了为NTP进行的动物工作外，我们还开始在NIEHS临床研究单位登记的人类受试者中进行研究，旨在将我们在动物身上的发现转化为经常使用NTP在啮齿动物模型中广泛分析的草药产品对人类的潜在生物学效应。

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 approach 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, approximately 11 microbial mutagenicity assays and 9 in vivo micronucleus assays have been initiated or completed. 40 in vivo Comet assays have been conducted in one or multiple tissues including blood, liver, kidney, stomach, colon, and brain. During the next fiscal year, additional emphasis is expected on in vitro measures of gene mutation and chromosomal damage so as to continue to reduce and refine our use of whole animal tests. 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 investigated 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 updated methods to streamline the assay have been developed, so that integration into existing toxicity tests can be more be accomplished. 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. Currently, 2 pig-a studies are planned, coupled with MN studies integrated into existing NTP toxicity studies. In addition to the animal work conducted for NTP, we have begun a study in human subjects enrolled at the NIEHS Clinical Research Unit aiming to translate our findings in animals to potential biological effects in humans who regularly use an herbal product that NTP is extensively analyzing in rodent models.