title: Evaluation of in vivo mutagenicity of isopropyl methanesulfonate by RBC Pig-a and PIGRET assays.
abstract: A comparison between the original red blood cell (RBC) Pig-a assay, which measures Pig-a mutant cells in RBCs, and the PIGRET assay, which uses reticulocytes, was conducted using the in vivo mutagenesis assay with isopropyl methanesulfonate (iPMS) as a part of a collaborative study by the Mammalian Mutagenicity Study Group in the Japanese Environmental Mutagen Society. Three dose levels of iPMS (50, 100, and 200mg/kg) were administered once intraperitoneally to 8-week-old male Crl:CD(SD) rats, and peripheral blood was sampled at 0 (1 day before dosing), and 1, 2, and 4 weeks after dosing with iPMS. As a result, a time-dependent increase in the mutant frequency of Pig-a mutant RBCs was observed in the RBC Pig-a assay, and a statistically significant increase was observed from 2 weeks after dosing. In the PIGRET assay, on the other hand, a statistically significant increase in Pig-a mutant frequency was obtained from 1 week after dosing at all dose levels, and the Pig-a mutant frequency at the highest dose level had already reached a plateau on week 1. The maximum Pig-a mutant frequency induced by a single treatment with iPMS at 200mg/kg in the PIGRET assay was approximately two times higher than that in the RBC Pig-a assay. These results indicate that the PIGRET assay can detect Pig-a mutants much earlier and with a higher value in Pig-a mutant frequency compared with the original RBC Pig-a assay, and it can enable judgement of mutagenicity of iPMS within 1 week after a single dose.
authors.affiliation: Medicinal Safety Research Laboratories, Daiichi Sankyo Co., Ltd., 1-16-13, Kitakasai, Edogawa-ku, Tokyo 134-8630, Japan. Electronic address: itoh.satoru.n5@daiichisankyo.co.jp.
authors.forename: Satoru
authors.initials: S
authors.lastname: Itoh
authors.affiliation: Biologics Pharmacology Research Laboratories, Daiichi Sankyo Co., Ltd., 1-2-58, Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan.
authors.forename: Chiharu
authors.initials: C
authors.lastname: Hattori
authors.affiliation: Medicinal Safety Research Laboratories, Daiichi Sankyo Co., Ltd., 1-16-13, Kitakasai, Edogawa-ku, Tokyo 134-8630, Japan.
authors.forename: Shiho
authors.initials: S
authors.lastname: Nakayama
authors.affiliation: Medicinal Safety Research Laboratories, Daiichi Sankyo Co., Ltd., 1-16-13, Kitakasai, Edogawa-ku, Tokyo 134-8630, Japan.
authors.forename: Akiharu
authors.initials: A
authors.lastname: Hanamoto
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000187:drug effects*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D008698:Mesylates / Q000633:toxicity*; D009152:Mutagenicity Tests / Q000379:methods*; D009153:Mutagens / Q000633:toxicity*; D051381:Rats; D012156:Reticulocytes / Q000187:drug effects*
chemical_list: D008565:Membrane Proteins; D008698:Mesylates; D009153:Mutagens; C080086:phosphatidylinositol glycan-class A protein; C002531:isopropylmethanesulfonate
keywords: In vivo mutation assay; Pig-a gene; Red blood cells; Reticulocytes