Evaluation for a Mutagenicity of 4,4′-Methylenedianiline on Hematopoietic Cells by a Pig-a Gene Mutation Assay in Rats

抄録

The Pig-a gene is involved in the synthesis of glycosylphosphatidylinositol (GPI) anchors. Pig-a gene mutations can be detected by identifying the presence of CD59, the GPI anchor protein, on the surface of erythrocytes (RBC Pig-a assay) and reticulocytes (PIGRET assay) and can be identified using flow cytometry. The usefulness of these Pig-a gene mutation assays has been confirmed in multi-laboratory trials with referenced mutagens. Although 4,4′-methylenedianiline (MDA) is an aromatic amine and has been identified as a potent hepatic carcinogen, in vivo micronucleus tests for MDA in hematopoietic cells determined that it was negative to weakly positive for genotoxicity. In the present study, we examined the mutagenicity of MDA in the peripheral blood of rats after 1- and 28-day MDA dosing using the Pig-a gene mutation assays. We also examined the utility of the RBC Pig-a and PIGRET assays. No changes in mutation frequency were observed after one-day MDA administration. Repeated dosing caused a moderate increase in mutation frequency compared to vehicle control at days 14 and 28, as measured by the RBC Pig-a assay and at day 14 by the PIGRET assay. The highest mutation frequency was found on days 7 and 14 by the PIGRET and RBC Pig-a assays, respectively.
In this study, we detected the mutagenicity of MDA in peripheral blood samples using gene mutation assays and judged to be positive for the MDA mutagenicity since a significant increase in mutation frequency was observed at high dose. These assays are expected to be easily integrated into general toxicity tests and to be combined with existing genotoxicity studies.