title: Evaluation of single-dose RBC Pig-a and PIGRET assays in detecting the mutagenicity of thiotepa in rats.
abstract: The Pig-a assay, which uses reticulocytes (PIGRET assay) as target cells, is anticipated to detect mutagenicity at earlier time points than the RBC Pig-a assay, which uses all red blood cells as target cells. As part of a collaborative study conducted by the Mammalian Mutagenicity Study (MMS) Group, we evaluated the PIGRET and RBC Pig-a assays to detect Pig-a gene mutations induced by the carcinogen thiotepa. A single dose of thiotepa at 7.5, 15, and 30mg/kg was administered to 8-week-old male Sprague-Dawley rats by oral gavage. PIGRET and RBC Pig-a assays were performed using peripheral blood collected from rats 7, 14, and 28days after thiotepa administration (Day 0 as the day of administration), and the resulting Pig-a mutant frequencies (MFs) were compared. Increased Pig-a MF was observed from Day 7 onwards using the PIGRET assay. Pig-a MF remained fairly constant thereafter until Day 28 in the 30mg/kg group, whereas it peaked on Day 14 in the 7.5 and 15mg/kg groups. Using the RBC Pig-a assay, on the other hand, no significant increase in MF was observed at any of the dosages on Days 7, 14, or 28. These findings show that Pig-a gene mutations following a single dose of thiotepa were detected using the PIGRET assay but not the RBC Pig-a assay, which suggests that PIGRET assay is more suitable than RBC Pig-a assay for evaluating the in vivo mutagenicity by a single dose.
authors.affiliation: Quality Assurance Division, Safety Science Institute, Suntory Business Expert Limited, 8-1-1 Seikadai, Seika-cho, Soraku-gun, Kyoto 619-0284, Japan.
authors.forename: Eri
authors.initials: E
authors.lastname: Tsutsumi
authors.affiliation: Quality Assurance Division, Safety Science Institute, Suntory Business Expert Limited, 8-1-1 Seikadai, Seika-cho, Soraku-gun, Kyoto 619-0284, Japan.
authors.forename: Ayaka
authors.initials: A
authors.lastname: Momonami
authors.affiliation: Quality Assurance Division, Safety Science Institute, Suntory Business Expert Limited, 8-1-1 Seikadai, Seika-cho, Soraku-gun, Kyoto 619-0284, Japan. Electronic address: Hisako_Hori@suntory.co.jp.
authors.forename: Hisako
authors.initials: H
authors.lastname: Hori
authors.affiliation: Quality Assurance Division, Safety Science Institute, Suntory Business Expert Limited, 8-1-1 Seikadai, Seika-cho, Soraku-gun, Kyoto 619-0284, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kitagawa
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004912:Erythrocytes / Q000187:drug effects*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D009152:Mutagenicity Tests / Q000379:methods*; D009153:Mutagens / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012156:Reticulocytes / Q000187:drug effects*; D013852:Thiotepa / Q000633:toxicity*
chemical_list: D008565:Membrane Proteins; D009153:Mutagens; C080086:phosphatidylinositol glycan-class A protein; D013852:Thiotepa
keywords: Gene mutation; Mutant frequency; PIGRET assay; RBC Pig-a assay; Thiotepa