1.1 本指南重点介绍了当前理解的一些更相关的生物学概念，并总结了当前感知和实践的可接受生物测定性能的关键技术方面。中国仓鼠卵巢细胞/次黄嘌呤鸟嘌呤磷酸核糖转移酶（CHO/HGPRT）测定 ( 1. ) 2. 已广泛应用于工业和环境化学品的毒理学评价。 1.2 本指南集中于细胞培养、诱变程序、数据分析、质量控制和测试策略的实际方面。建议的方法代表了专家组成员对分析性能的共识。 然而，应当理解的是，这些仅仅是一般性的指导方针，在没有使用可靠的科学判断的情况下，是不能遵循的。分析用户应根据待测物质的性质和待回答的问题来评估其方法。 1.3 偏离基于合理科学判断的准则绝不应使获得的结果无效。 1.4 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.5 本标准并非旨在解决与其使用相关的所有安全问题（如有）。 本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.6 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 2.1 CHO/HGPRT分析检测X-连锁次黄嘌呤的正向突变- 中国仓鼠卵巢（CHO）细胞中的鸟嘌呤磷酸核糖转移酶（hgprt）位点（编码该酶，hgprt）。将最初来源于中国仓鼠卵巢组织的细胞暴露于供试品中，并遵循适当的细胞培养方案，监测原始治疗群体的后代是否存在功能性HGPRT的丢失，这可能是由于突变所致。对嘌呤类似物6-硫鸟嘌呤（6TG）（或不太理想的8-氮杂鸟嘌呤（8AG））的抗性被用作遗传标记。HGPRT催化无毒6TG转化为其有毒的核糖磷酸化衍生物。因此，这种酶或其活性的丧失会导致细胞对6TG产生耐药性。 2.2 由于HGPRT是嘌呤核苷酸补救途径的一种酶，酶的丢失不是致命事件。理论上，在hgprt位点可以检测到不同类型的突变事件（碱基替换、移码、缺失、某些染色体类型的损伤等）。CHO/HGPRT分析已用于研究广泛的诱变剂，包括辐射 ( 2- 4. ) ，以及各种各样的化学品 ( 1. ) ，以及复杂的化学混合物 ( 5. ) .

1.1 This guide highlights some of the more relevant biological concepts as they are currently understood, and summarizes the critical technical aspects for acceptable bioassay performances as they currently are perceived and practiced. The Chinese hamster ovary cell/hypoxanthine guanine phosphoribosyl transferase (CHO/HGPRT) assay ( 1 ) 2 has been widely applied to the toxicological evaluation of industrial and environmental chemicals. 1.2 This guide concentrates on the practical aspects of cell culture, mutagenesis procedures, data analysis, quality control, and testing strategy. The suggested approach represents a consensus of the panel members for the performance of the assay. It is to be understood, however, that these are merely general guidelines and are not to be followed without the use of sound scientific judgement. Users of the assay should evaluate their approach based on the properties of the substances to be tested and the questions to be answered. 1.3 Deviation from the guidelines based on sound scientific judgement should by no means invalidate the results obtained. 1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 2.1 The CHO/HGPRT assay detects forward mutations of the X-linked hypoxanthine-guanine phosphoribosyl transferase (hgprt) locus (coding for the enzyme, HGPRT) in Chinese hamster ovary (CHO) cells. Cells originally derived from Chinese hamster ovary tissue are exposed to a test article and, following an appropriate cell culture regimen, descendants of the original treated population are monitored for the loss of functional HGPRT, presumably due to mutations. Resistance to a purine analogue, 6-thioguanine (6TG) (or less desirably, 8-azaguanine (8AG)), is employed as the genetic marker. HGPRT catalyzes the conversion of the nontoxic 6TG to its toxic ribophosphorylated derivative. Loss of the enzyme or its activity therefore leads to cells resistant to 6TG. 2.2 Because HGPRT is an enzyme of the purine nucleotide salvage pathway, loss of the enzyme is not a lethal event. Different types of mutational events (base substitutions, frameshifts, deletions, some chromosomal type lesions, and so forth) should theoretically be detectable at the hgprt locus. The CHO/HGPRT assay has been used to study a wide range of mutagens, including radiations ( 2- 4 ) , and a wide variety of chemicals ( 1 ) , and complex chemical mixtures ( 5 ) .