The Pig-a assay, which uses reticulocytes (PIGRET assay) as target cells, is anticipated to detect mutagenicity at earlier time points than the RBC Pig-a assay, which uses all red blood cells as target cells. As part of a collaborative study conducted by the Mammalian Mutagenicity Study (MMS) Group, we evaluated the PIGRET and RBC Pig-a assays to detect Pig-a gene mutations induced by the carcinogen thiotepa. A single dose of thiotepa at 7.5, 15, and 30mg/kg was administered to 8-week-old male Sprague-Dawley rats by oral gavage. PIGRET and RBC Pig-a assays were performed using peripheral blood collected from rats 7, 14, and 28days after thiotepa administration (Day 0 as the day of administration), and the resulting Pig-a mutant frequencies (MFs) were compared. Increased Pig-a MF was observed from Day 7 onwards using the PIGRET assay. Pig-a MF remained fairly constant thereafter until Day 28 in the 30mg/kg group, whereas it peaked on Day 14 in the 7.5 and 15mg/kg groups. Using the RBC Pig-a assay, on the other hand, no significant increase in MF was observed at any of the dosages on Days 7, 14, or 28. These findings show that Pig-a gene mutations following a single dose of thiotepa were detected using the PIGRET assay but not the RBC Pig-a assay, which suggests that PIGRET assay is more suitable than RBC Pig-a assay for evaluating the in vivo mutagenicity by a single dose.

中文翻译：

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单剂量 RBC Pig-a 和 PIGRET 测定在检测大鼠噻替哌的致突变性中的评价。

Pig-a 检测使用网织红细胞（PIGRET 检测）作为靶细胞，预计比 RBC Pig-a 检测在更早的时间点检测致突变性，RBC Pig-a 检测使用所有红细胞作为靶细胞。作为哺乳动物致突变性研究 (MMS) 小组开展的一项合作研究的一部分，我们评估了 PIGRET 和 RBC Pig-a 检测，以检测致癌物质噻替哌诱导的 Pig-a 基因突变。8 周龄雄性 Sprague-Dawley 大鼠通过灌胃给予单剂量的噻替哌 7.5、15 和 30mg/kg。PIGRET 和 RBC Pig-a 测定是使用从 thiotepa 给药后第 7、14 和 28 天（第 0 天作为给药日）收集的大鼠外周血进行的，并比较所得的 Pig-a 突变频率（MF）。从第 7 天起，使用 PIGRET 测定法观察到 Pig-a MF 增加。Pig-a MF此后在30mg/kg组中保持相当稳定直到第28天，而在7.5和15mg/kg组中在第14天达到峰值。另一方面，使用 RBC Pig-a 测定，在第 7、14 或 28 天的任何剂量下均未观察到 MF 显着增加。这些发现表明，单剂量噻替哌后 Pig-a 基因突变是使用 PIGRET 试验检测而不是 RBC Pig-a 试验，这表明 PIGRET 试验比 RBC Pig-a 试验更适合评估单剂量的体内致突变性。