Evaluation of the mutagenicity of alkylating agents, methylnitrosourea and temozolomide, using the rat Pig-a assay with total red blood cells or reticulocytes

•Mutagenicity of methylnitrosourea and temozolomide were examined with Pig-a assay.•Methylnitrosourea and temozolomide increased Pig-a mutants in RBCs and RETs.•PIGRET assay can detect mutagenicity more sensitively than the RBC Pig-a assay.

A collaborative study of the endogenous phosphatidylinositol glycan class A (Pig-a) gene mutation assay was conducted by the Japanese Environmental Mutagen Society/Mammalian Mutagenicity Study Group with a single-dosing regimen of test chemicals administered to male rats. As a part of the study, two DNA alkylating agents, methylnitrosourea (MNU) and temozolomide (TMZ), were dosed by single oral gavage at 25, 50, and 100 mg/kg body weight. Pig-a mutant analysis of total red blood cells (RBCs; RBC Pig-a assay) and reticulocytes (RETs; PIGRET assay) was performed on Days 8, 15 and 29 after the administration. Both chemicals increased Pig-a mutants among RBCs and RETs with dose dependency on all days examined. The mutant frequencies were higher among RETs compared with RBCs, indicating that the PIGRET assay could detect mutagenicity more sensitively than the RBC Pig-a assay after a single dose of test chemicals.