title: Absence ofin vivomutagenicity of multi-walled carbon nanotubesinsingle intratracheal instillation study using F344gptdelta rats.
abstract: BACKGROUND
  It is known that fibrous particles of micrometer length, such as carbon nanotubes, which have same dimensions as asbestos, are carcinogenic. Carcinogenicity of nanomaterials is strongly related to inflammatory reactions; however, the genotoxicity mechanism(s) is unclear. Indeed, inconsistent results on genotoxicity of multi-walled carbon nanotubes (MWCNTs) have been shown in several reports. Therefore, we analyzed the in vivo genotoxicity induced by an intratracheal instillation of straight MWCNTs in rats using a different test system-thePig-agene mutation assay-that can reflect the genotoxicity occurring in the bone marrow. Since lungs were directly exposed to MWCNTs upon intratracheal instillation, we also performed thegptassay using the lungs.
  
  
  RESULTS
  We detected no significant differences inPig-amutant frequencies (MFs) between the MWCNT-treated and control rats. Additionally, we detected no significant differences ingptMFs in the lung between the MWCNT-treated and control rats.
  
  
  CONCLUSIONS
  Our findings indicated that a single intratracheal instillation of MWCNTs was non-mutagenic to both the bone marrow and lung of rats.
authors.affiliation: Division of Genetics and Mutagenesis, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo, 158-8501 Japan.
authors.forename: Katsuyoshi
authors.identifier: 0000-0002-0866-5504
authors.initials: K
authors.lastname: Horibata
authors.affiliation: Division of Genetics and Mutagenesis, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo, 158-8501 Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Ukai
authors.affiliation: Department of Pharmaceutical and Environmental Sciences, Tokyo Metropolitan Institute of Public Health, 3-24-1 Hyakunin-cho, Shinjuku, Tokyo, 169-0073 Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Ogata
authors.affiliation: Department of Pharmaceutical and Environmental Sciences, Tokyo Metropolitan Institute of Public Health, 3-24-1 Hyakunin-cho, Shinjuku, Tokyo, 169-0073 Japan ; Present address: Department of Nutritional Science and Food Safety, Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakura-ga-Oka, Setagaya, Tokyo, 156-8502 Japan.
authors.forename: Dai
authors.initials: D
authors.lastname: Nakae
authors.affiliation: Department of Pharmaceutical and Environmental Sciences, Tokyo Metropolitan Institute of Public Health, 3-24-1 Hyakunin-cho, Shinjuku, Tokyo, 169-0073 Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ando
authors.affiliation: Department of Pharmaceutical and Environmental Sciences, Tokyo Metropolitan Institute of Public Health, 3-24-1 Hyakunin-cho, Shinjuku, Tokyo, 169-0073 Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kubo
authors.affiliation: Department of Pharmaceutical and Environmental Sciences, Tokyo Metropolitan Institute of Public Health, 3-24-1 Hyakunin-cho, Shinjuku, Tokyo, 169-0073 Japan.
authors.forename: Akemichi
authors.initials: A
authors.lastname: Nagasawa
authors.affiliation: Department of Pharmaceutical and Environmental Sciences, Tokyo Metropolitan Institute of Public Health, 3-24-1 Hyakunin-cho, Shinjuku, Tokyo, 169-0073 Japan.
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Yuzawa
authors.affiliation: Division of Genetics and Mutagenesis, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo, 158-8501 Japan.
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Honma
keywords: Carbon nanoparticle; Multi-walled carbon nanotubes; Pig-a gene mutation assay; in vivo genotoxicity