MNNG-induced mutations in the adult gill and hepatopancreas and in embryos of rpsL transgenic zebrafish.
To evaluate the feasibility of a mutagenicity assay using adult rpsL transgenic zebrafish, 4- to 8-month-old females were exposed to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) (0, 15 or 30 mg/L in a water bath for 2 h). At 2 weeks after exposure, MNNG showed a concentration-dependent significant increase in mutant frequency (MF) of 8 x 10(-5), 18 x 10(-5), and 51 x 10(-5), respectively, in the gill. DNA sequencing revealed that 60-74% of the induced mutations were G:C to A:T transitions, consistent with the known mutagenic effects of MNNG. A marginal but significant increase in MF was observed in the hepatopancreas only in the group exposed to 30 mg/L, with the induction of some G:C to A:T transitions. A time-course of the appearance of mutations was determined in fish treated with 15 mg/L MNNG. In both, the gill and hepatopancreas, a higher MF was observed at 3 weeks than at 2 weeks, suggesting that an expression time of at least 3 weeks is preferable for the assay. When embryos (29 h post-fertilization) were exposed to MNNG (0, 50, and 150 mg/L) for 1 h, MFs increased significantly with an increase in the concentration of MNNG (5 x 10(-5), 40 x 10(-5), and 144 x 10(-5), respectively) at 3 days after exposure. G:C to A:T transitions were the predominant mutations, and these occurred at the same sites in the rpsL gene as in adult tissues. Thus, MNNG induces typical mutations in the gill and hepatopancreas of adult fish, and in embryos, suggesting that the rpsL zebrafish is a useful tool for monitoring genotoxicity caused by water-borne mutagens.
Amanuma
Kimiko
K
Research Center for Environmental Risk, National Institute for Environmental Studies, Onogawa, Tsukuba 305-8506, Japan. amanuma@nies.go.jp
Nakamura
Takashi
T
Aoki
Yasunobu
Y
D000818:Animals; D030801:Animals, Genetically Modified; D004305:Dose-Response Relationship, Drug; D005880:Gills / Q000187:drug effects* / Q000378:metabolism; D043143:Hepatopancreas / Q000187:drug effects* / Q000378:metabolism; D008769:Methylnitronitrosoguanidine / Q000633:toxicity*; D009153:Mutagens / Q000633:toxicity*; D015027:Zebrafish / Q000196:embryology*
D009153:Mutagens; D008769:Methylnitronitrosoguanidine