Prolonged rest period enables the detection of micronucleated hepatocytes in the liver of young adult rats after a single dose of diethylnitrosamine or mitomycin C.
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.
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.
Keisuke
K
Shimada
Drug Safety Research Laboratories, Astellas Pharma Inc., 2-1-6 Kashima Yodogawa-ku, Osaka 532-8514, Japan.
Mika
M
Yamamoto
Drug Safety Research Laboratories, Astellas Pharma Inc., 2-1-6 Kashima Yodogawa-ku, Osaka 532-8514, Japan.
Miyuki
M
Takashima
Drug Safety Research Laboratories, Astellas Pharma Inc., 2-1-6 Kashima Yodogawa-ku, Osaka 532-8514, Japan; Present address: Research Administration Office, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan.
Jiro
J
Seki
Drug Safety Research Laboratories, Astellas Pharma Inc., 2-1-6 Kashima Yodogawa-ku, Osaka 532-8514, Japan; Present address: Drug Safety Research Laboratories, Shin Nippon Biomedical Laboratories, Ltd., 2-1-1 Fushimi-machi, Chuo-ku, Osaka 541-0044, Japan.
Yoichi
Y
Miyamae
Drug Safety Research Laboratories, Astellas Pharma Inc., 2-1-6 Kashima Yodogawa-ku, Osaka 532-8514, Japan. Electronic address: akihiro.wakata@astellas.com.
Akihiro
A
Wakata
D000284:Administration, Oral; D000818:Animals; D004249:DNA Damage; D004052:Diethylnitrosamine / Q000008:administration & dosage / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D022781:Hepatocytes / Q000187:drug effects*; D007274:Injections, Intraperitoneal; D015162:Micronucleus Tests / Q000379:methods; D016685:Mitomycin / Q000008:administration & dosage / Q000633:toxicity*; D009153:Mutagens / Q000008:administration & dosage / Q000633:toxicity*; D051381:Rats
D009153:Mutagens; D004052:Diethylnitrosamine; D016685:Mitomycin
Diethylnitrosamine; Liver micronucleus assay; Mitomycin C; Positive control for a repeated-dose liver micronucleus assay; Single-dose administration