GENETIC TOXICITY IN BACTERIA AND RODENTS

遗传毒性测试合同规定评估接触国家毒理学方案正在研究的化合物可能产生的不利遗传影响。采用的测试系统包括体外（基于动物细胞和细菌）和体内（大鼠和小鼠）测定。常规进行三项主要试验：体外细菌致突变性试验、体内啮齿动物外周血微核（MN）试验和体内啮齿动物多种组织DNA损伤（彗星）试验。MN检测试剂盒现在通常通过对制备的血液样本进行流式细胞术分析而不是通过对载玻片进行评分来收集数据。这一创新提高了检测诱发染色体损伤的能力，提高了检测的客观性和数据收集的速度。MN和彗星试验通常用同一组动物进行，从而最大限度地从单个治疗动物收集数据，减少动物使用，并降低成本。在上一财年，启动或完成了18项微生物致突变性试验和26项体内微核试验。已在一种或多种组织（包括血液、肝脏、肾脏、胃、结肠和大脑）中进行了12次体内彗星试验。此外，已经进行了体外彗星试验来比较几种不同细胞系之间的DNA修复活性，以更好地理解与特定癌症相关的某些突变基因的作用。在下一个财政年度，预计将进一步强调基因突变和染色体损伤的体外测量，以便继续减少和改进我们对整个动物试验的使用。在过去的财政年度中，在检测实验室中研究了另一种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：猪-a突变试验（磷脂酰肌醇聚糖锚生物合成，A类基因）。该基因的突变很容易在实验室啮齿动物的红细胞样本中检测到，并且已经开发了简化检测的更新方法，以便更好地整合到现有的毒性测试中。在下一个财政年度，我们将尝试将该试验与体内MN和彗星试验进行复合，增加我们从试验动物中获得的遗传毒性信息，以提供更全面的化学品遗传毒性潜力概况。

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, 18 microbial mutagenicity assays and 26 in vivo micronucleus assays have been initiated or completed. Twelve in vivo Comet assays have been conducted in one or multiple tissues including blood, liver, kidney, stomach, colon, and brain. In addition, in vitro Comet assays have been conducted 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. During the next fiscal year, additional emphasis is expected on in vitro measures of gene mutation and chromosomal damageso 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.