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International Pig‐a gene mutation assay trial (Stage III): Results with N ‐methyl‐ N ‐nitrosourea
Author(s) -
Lynch Anthony M.,
Giddings Amanda,
Custer Laura,
Gleason Carol,
Henwood Andrew,
Aylott Mike,
Kenny Julia
Publication year - 2011
Publication title -
environmental and molecular mutagenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 87
eISSN - 1098-2280
pISSN - 0893-6692
DOI - 10.1002/em.20691
Subject(s) - genotoxicity , micronucleus test , comet assay , hematology , gene mutation , bone marrow , micronucleus , toxicity , microbiology and biotechnology , ethyl methanesulfonate , nitrosourea , pharmacology , andrology , biology , mutation , dna damage , chemistry , medicine , genetics , gene , dna , chemotherapy
N ‐methyl‐ N ‐nitrosourea (MNU) was evaluated in the in vivo Pig‐a mutation assay as part of an International Collaborative Trial to investigate laboratory reproducibility, 28‐day study integration, and comparative analysis with micronucleus (MN), comet, and clinical pathology endpoints. Male Sprague Dawley rats were treated for 28 days with doses of 0, 2.5, 5, and 10 mg MNU/kg/day in two independent laboratories, GlaxoSmithKline (GSK) and Bristol Myers Squibb (BMS). Additional studies investigated the low‐dose region (<2.5 mg/kg/day). Reticulocytes were evaluated for Pig‐a phenotypic mutation, CD59‐negative reticulocytes/erythrocytes (RETs CD59− / RBCs CD59− ) on Days 1, 4, 15, 29, 43, and 57, and for micronucleated reticulocytes (MN‐RETs) on Days 4 and 29. Comet analysis was conducted for liver and whole blood, and hematology and clinical chemistry was investigated. Dose‐dependent increases in the frequency of RETs CD59− and RBCs CD59− were observed by Day 15 or 29, respectively. Dose‐dependent increases were observed in %MN‐RET on Days 4 and 29, and in mean %tail intensity in liver and in blood. Hematology/clinical chemistry data demonstrated bone marrow toxicity. Data comparison between GSK and BMS indicated a high degree of concordance with the Pig‐a mutation assay results, consistent with previous observations with MNU and N ‐ethyl‐ N ‐nitrosourea. These data confirm that complementary genotoxicity endpoints can be effectively incorporated into routine toxicology studies, a strategy that can provide information on gene mutation, chromosome damage, and DNA strand breaks in a single repeat dose rodent study. Collectively, this would reduce animal usage while providing valuable genetic toxicity information within the context of other toxicological endpoints. Environ. Mol. Mutagen., 2011. © 2011 Wiley‐Liss, Inc.