The in vivo Pig-a assay is being used in safety studies to evaluate the potential of chemicals to induce somatic cell gene mutations. Ongoing work is aimed at developing an Organisation for Economic Cooperation and Development (OECD) test guideline to support routine use for regulatory purposes (OECD project number 4.93). Among the details that will need to be articulated in an eventual guideline are recommended treatment and harvest schedules. With this in mind, experiments reported herein were performed with Wistar Han rats exposed to aristolochic acid I (AA), 1,3-propane sultone, chlorambucil, thiotepa or melphalan using each of two commonly used treatment schedules: 3 or 28 consecutive days. In the case of the 3-day studies, blood was collected for Pig-a analysis on days 15 or 16 and 29 or 30. For the 28-day studies blood was collected on day 29 or 30. The effect of treatment on mutant reticulocytes and mutant erythrocytes was evaluated with parametric pair-wise tests. While each of the five mutagens increased mutant phenotype cell frequencies irrespective of study design, statistical significance was consistently achieved at lower dose levels when the 28-day format was used (e.g. 2.75 vs 20 mg/kg/bw for AA). To more thoroughly investigate the dose–response relationships, benchmark dose (BMD) analyses were performed with PROAST software. These results corroborate the pair-wise testing results in that lower BMD values were obtained with the 28-day design. Finally, mutagenic potency, as measured by BMD analyses, most consistently correlated with the mutagens’ tumorigenic dose 50 values when the lengthier treatment schedule was used. Collectively, these results suggest that both 3- and 28-day treatment schedules have merit in hazard identification-type studies. That being said, for the purpose of regulatory safety assessments, there are clear advantages to study designs that utilise protracted exposures.

中文翻译：

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猪基因突变试验研究设计：3天和28天重复剂量治疗方案的关键评估。

的体内PIG-A测定在安全性研究被用于评价化学品的潜在诱导体细胞基因突变。正在进行的工作旨在制定经济合作与发展组织（OECD）的测试指南，以支持出于监管目的的常规使用（OECD项目编号4.93）。在最终指南中需要阐明的细节中，包括推荐的处理和收割时间表。考虑到这一点，本文报道的实验是使用两个常用治疗方案（连续3天或28天）中的每一个对暴露于马兜铃酸I（AA），1,3-丙烷磺酸内酯，苯丁酸氮芥，噻替帕或美法仑的Wistar Han大鼠进行的。在为期3天的研究中，为猪-a采集了血液在第15天或第16天和第29天或第30天进行分析。对于第28天的研究，在第29天或第30天收集血液。通过参数对测试评估了治疗对突变型网状细胞和突变型红细胞的影响。尽管五种诱变剂均增加突变表型细胞的频率，而与研究设计无关，但当使用28天剂量时（例如AA为2.75 vs 20 mg / kg / bw），在较低剂量水平下即可始终达到统计学显着性。为了更彻底地研究剂量-反应关系，使用PROAST软件进行了基准剂量（BMD）分析。这些结果证实了成对的测试结果，因为28天的设计获得了较低的BMD值。最后，通过BMD分析测得的致突变力，当使用更长的治疗方案时，与诱变剂的致瘤剂量50值最一致。总体而言，这些结果表明3天和28天的治疗方案在危害识别类型研究中均具有优势。话虽如此，出于监管安全性评估的目的，研究使用长期暴露的设计具有明显的优势。