2014 Volume 36 Issue 4 Pages 186-190
A recent report on an interlaboratory trial on the Pig-a mutation assays using an antibody against the erythroid marker (HIS49 Pig-a assays) has shown transferability and reproducibility of the assays. In this report, methyl methanesulfonate (MMS) was used to further evaluate the ability of HIS49 Pig-a assays in different study designs (28-day repeated dose and single dose). MMS was administered to male Sprague Dawley (SD) rats orally for 28 days at a dose of 7.5, 15, or 30 mg/kg/day or by single oral gavage at 50, 100 and 200 mg/kg in 28-day study and single dose study, respectively. Pig-a assays for total red blood cells (RBC Pig-a assay), for reticulocytes (PIGRET assay) and micronucleated reticulocytes (MN-RET) measurement were performed. In the 28-day study, there were significant increases in the Pig-a mutant frequency (Pig-a MF) in PIGRET assay at 30 mg/kg/day on Days 8, 15 and 29 with the maximum Pig-a MF on Day 29. On the contrary, there was no change in the Pig-a MF in RBC Pig-a assay. In the single dose study, MMS resulted in a steady increase in Pig-a MF in PIGRET assay from Day 8 through to Day 29 and a delayed increase in Pig-a MF in RBC Pig-a assay at Day 15 and 29 with maximam Pig-a MF on Day 29. MMS also induced significant increases in the MN-RET frequency on Day 4 of the 28-day study and on Day 3 of the single dose study. These results suggest that the PIGRET assay has the following advantages. The accumulated properties with repeated doses would be useful when the assay is integrated with a repeated dose general toxicity study, and the rapid detection of mutagenesis using a single dose protocol would be useful for early assessment of the in vivo mutagenicity of chemicals.