{"title":"The effect of aging on the repeated-dose liver micronucleus assay.","authors":"Miyuki Shigano, Hironao Takasawa, Shuichi Hamada","doi":"10.1186/s41021-021-00212-3","DOIUrl":null,"url":null,"abstract":"<p><strong>Background: </strong>The liver micronucleus (MN) assay is an effective and important in vivo test for detecting genotoxic compounds. In particular, the repeated-dose liver MN (RDLMN) assay which greatly facilitates incorporation of the liver MN assay into the general toxicity study has been developed. Usefulness of the RDLMN assay was appraised highly in the 7th International Workshops on Genotoxicity Testing (2017 in Tokyo) in that sufficient numbers and types of chemicals were studied and easy integration into the general toxicity study is preferred from the 3R's point of view. However, it was pointed out that it is necessary to evaluate the effect of age at the start of 4-week repeated administration, since there are limited data, where only those of rats of 6 week of age at the start of administration are available. In this study, we conducted the 4-week RDLMN assay using rats of 6 and 8 weeks of age (at the start of administration) to investigate the effect of age on the liver MN inducibility. Clofibrate, a weak inducer of liver MN, was used in this study to detect the slight difference in the liver MN induction.</p><p><strong>Results: </strong>The liver MN induced by clofibrate was detected in both rats of 6 and 8 weeks of age at the start of administration. However, the liver MN induction was lower in rats of 8 weeks of age compared to rats of 6 weeks of age at the start of administration.</p><p><strong>Conclusion: </strong>These results suggest that the liver MN inducibility decreases with age. Therefore, we recommend the use of rats of 6 weeks of age at start of administration to reliably detect the liver MN induction in the RDLMN assay.</p>","PeriodicalId":12709,"journal":{"name":"Genes and Environment","volume":" ","pages":"37"},"PeriodicalIF":2.7000,"publicationDate":"2021-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8427953/pdf/","citationCount":"2","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Genes and Environment","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1186/s41021-021-00212-3","RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GENETICS & HEREDITY","Score":null,"Total":0}
引用次数: 2
Abstract
Background: The liver micronucleus (MN) assay is an effective and important in vivo test for detecting genotoxic compounds. In particular, the repeated-dose liver MN (RDLMN) assay which greatly facilitates incorporation of the liver MN assay into the general toxicity study has been developed. Usefulness of the RDLMN assay was appraised highly in the 7th International Workshops on Genotoxicity Testing (2017 in Tokyo) in that sufficient numbers and types of chemicals were studied and easy integration into the general toxicity study is preferred from the 3R's point of view. However, it was pointed out that it is necessary to evaluate the effect of age at the start of 4-week repeated administration, since there are limited data, where only those of rats of 6 week of age at the start of administration are available. In this study, we conducted the 4-week RDLMN assay using rats of 6 and 8 weeks of age (at the start of administration) to investigate the effect of age on the liver MN inducibility. Clofibrate, a weak inducer of liver MN, was used in this study to detect the slight difference in the liver MN induction.
Results: The liver MN induced by clofibrate was detected in both rats of 6 and 8 weeks of age at the start of administration. However, the liver MN induction was lower in rats of 8 weeks of age compared to rats of 6 weeks of age at the start of administration.
Conclusion: These results suggest that the liver MN inducibility decreases with age. Therefore, we recommend the use of rats of 6 weeks of age at start of administration to reliably detect the liver MN induction in the RDLMN assay.
期刊介绍：
Genes and Environment is an open access, peer-reviewed journal that aims to accelerate communications among global scientists working in the field of genes and environment. The journal publishes articles across a broad range of topics including environmental mutagenesis and carcinogenesis, environmental genomics and epigenetics, molecular epidemiology, genetic toxicology and regulatory sciences.
Topics published in the journal include, but are not limited to, mutagenesis and anti-mutagenesis in bacteria; genotoxicity in mammalian somatic cells; genotoxicity in germ cells; replication and repair; DNA damage; metabolic activation and inactivation; water and air pollution; ROS, NO and photoactivation; pharmaceuticals and anticancer agents; radiation; endocrine disrupters; indirect mutagenesis; threshold; new techniques for environmental mutagenesis studies; DNA methylation (enzymatic); structure activity relationship; chemoprevention of cancer; regulatory science. Genetic toxicology including risk evaluation for human health, validation studies on testing methods and subjects of guidelines for regulation of chemicals are also within its scope.
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