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Novel transgenic rat for in vivo genotoxicity assays using 6‐thioguanine and Spi − selection
Author(s) -
Hayashi Hiroyuki,
Kondo Hiroshi,
Masumura Kenichi,
Shindo Yasuhiro,
Nohmi Takehiko
Publication year - 2003
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.10152
Subject(s) - ethylnitrosourea , genotoxicity , in vivo , mutagen , microbiology and biotechnology , mutant , biology , benzo(a)pyrene , transgene , carcinogen , gene , chemistry , genetics , toxicity , organic chemistry
Transgenic rodents are valuable models for investigating the genotoxicity of chemicals in vivo. Here, we report the establishment of a novel transgenic rat for genotoxicity analysis. In this model, about 10 copies of λEG10 DNA carrying the gpt gene of E. coli and the red/gam genes of λ phage are integrated per haploid genome of Sprague‐Dawley rats at position 4q24‐q31. After recovery of λEG10 phage, point mutations in the gpt gene and deletions in the red/gam genes are identified by 6‐thioguanine and Spi − selection, respectively. To examine the suitability of these rats for performing in vivo mutagenicity assays, rats were treated with single intraperitoneal injections of ethylnitrosourea (ENU; 100 mg/kg) or benzo[ a ]pyrene (B[ a ]P; 62.5 and 125 mg/kg), and the mutant frequencies (MFs) in the liver were determined 7 days after the treatment. ENU enhanced the gpt MF about 7‐fold over the control while it did not significantly increase the Spi − MF. B[ a ]P increased both the gpt and Spi − MFs several‐fold in a dose‐dependent manner. To examine the kinetics of MF, ENU was administered (50 mg/kg/day for 5 successive days) and gpt MFs in the liver were determined 7, 21, 35, and 70 days after the last injection. The MF increased to 8‐fold and 13‐fold over the control at 7 and 35 days, respectively, after the last injection and then slightly declined at 70 days. These kinetics are similar to those reported for ENU‐treated lacZ transgenic mice. This novel transgenic rat could be useful for investigating species differences between rats and mice in their response to genotoxic agents. Environ. Mol. Mutagen. 41:253–259, 2003. © 2003 Wiley‐Liss, Inc.