Shimada Keisuke, Yamamoto Mika, Takashima Miyuki, Seki Jiro, Miyamae Yoichi, Wakata Akihiro
Drug Safety Research Laboratories, Astellas Pharma Inc., 2-1-6 Kashima Yodogawa-ku, Osaka 532-8514, Japan; Present address: Laboratory of Laboratory Animal Science and Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo 060-0818, Japan.
Drug Safety Research Laboratories, Astellas Pharma Inc., 2-1-6 Kashima Yodogawa-ku, Osaka 532-8514, Japan.
Mutat Res Genet Toxicol Environ Mutagen. 2015 Sep;791:38-41. doi: 10.1016/j.mrgentox.2015.07.010. Epub 2015 Jul 28.
A repeated-dose micronucleus assay utilizing young adult rat hepatocytes was recently developed to evaluate the genotoxicity. In this assay, accumulation of micronucleated hepatocytes (MNHEPs) induced by repeated dosing of genotoxic chemicals is considered to be a key factor in the detection of micronuclei induction. Then, we hypothesized that the period following chemical exposure enable the detection of MNHEP induction in young adult rats, namely that MNHEPs can be generated from chromosomally damaged cells and accumulate following initiation of chemical exposure until sampling. We therefore measured MNHEP induction at 2 or 4 weeks after a single oral administration of 12.5, 50, or 100mg/kg of diethylnitrosamine (DEN) or an intraperitoneal administration of 0.5, 1.0, or 2.0mg/kg of mitomycin C (MMC) to young adult rats. Results showed a statistically significant, dose-dependent increase in the numbers of MNHEPs in DEN- or MMC-treated rats, indicating that prolonged rest period following a single dose of a genotoxic chemical enables the detection of MNHEP induction in the liver of young adult rats. From these results, a single oral administration of 50mg/kg of DEN with a 2- or 4- week rest period can be used as a positive control in repeated-dose liver micronucleus assays. This procedure is superior in terms of labor saving and animal welfare to repeated dosing of DEN.
最近开发了一种利用年轻成年大鼠肝细胞的重复剂量微核试验来评估遗传毒性。在该试验中，遗传毒性化学物质重复给药诱导的微核化肝细胞（MNHEP）的积累被认为是检测微核诱导的关键因素。然后，我们假设化学物质暴露后的时间段能够检测年轻成年大鼠中MNHEP的诱导情况，即MNHEP可由染色体受损细胞产生，并在化学物质暴露开始后直至采样时积累。因此，我们对年轻成年大鼠单次口服12.5、50或100mg/kg二乙基亚硝胺（DEN）或腹腔注射0.5、1.0或2.0mg/kg丝裂霉素C（MMC）后2周或4周时的MNHEP诱导情况进行了测量。结果显示，DEN或MMC处理的大鼠中MNHEP数量有统计学意义的剂量依赖性增加，表明单次给予遗传毒性化学物质后延长的休息期能够检测年轻成年大鼠肝脏中MNHEP的诱导情况。根据这些结果，单次口服50mg/kg DEN并休息2周或4周可作为重复剂量肝脏微核试验的阳性对照。该方法在节省劳动力和动物福利方面优于DEN重复给药。
