Evaluation of red blood cell Pig-a assay and PIGRET assay in rats using chlorambucil

- RBC Pig-a assay and PIGRET assay detected the mutagenicity of chlorambucil.
- In the RBC Pig-a assay, significant increases in MFs were observed on Day 15.
- In the PIGRET assay, MFs increased significantly on Day 8.
- The PIGRET assay may detect the mutagenicity earlier than the RBC Pig-a assay.

The Pig-a assay is a novel method to assess the in vivo mutagenicity of compounds, and it is expected to be useful for the detection of genotoxicity. In this study, to assess the performance of the Pig-a assay targeting red blood cells (RBCs; RBC Pig-a assay) and reticulocytes (RETs; PIGRET assay), chlorambucil, which is a genotoxicant, was orally administered to male rats once at 10, 20 and 40 mg/kg on Day 1, and the mutant frequencies (MFs) of RBCs and RETs were examined periodically. In the RBC Pig-a assay, significant increases in MFs were observed at 40 mg/kg on Day 15 and at 20 mg/kg or higher on Day 29. In the PIGRET assay, MFs increased significantly at all dose levels on Day 8 and only at 20 mg/kg on Day 15, but there was no increase in MFs in the treatment groups on Day 29. In conclusion, the RBC Pig-a assay and PIGRET assay in rats have sufficient sensitivity to detect the mutagenicity of chlorambucil, and the PIGRET assay could detect its mutagenicity earlier and at a lower dose than the RBC Pig-a assay.