Premium
Dose‐ and time‐dependent responses for micronucleus induction by X‐rays and fast neutrons in gill cells of medaka ( Oryzias latipes )
Author(s) -
Takai Akinori,
Kagawa Nao,
Fujikawa Kazuo
Publication year - 2004
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.20042
Subject(s) - oryzias , micronucleus , micronucleus test , biology , neutron , relative biological effectiveness , toxicology , irradiation , chemistry , genetics , toxicity , physics , gene , nuclear physics , organic chemistry
Medaka fish ( Oryzias latipes ) were exposed to various doses of X‐rays or fast neutrons, and the frequency of micronucleated cells (MNCs) was measured in gills sampled at 12‐ or 24‐hr intervals from 12 to 96 hr after exposure. The resulting time course of MNC frequency was biphasic, with a clear peak 24 hr after exposure, irrespective of the kind of radiation applied and the dose used. The half‐life of MNCs induced in the gill tissues by the two exposures fluctuated around 28 hr, with no significant dose‐dependent trend for either X‐ray‐ or neutron‐exposed fish. As assayed 24 hr after exposure, the MNC frequency increased linearly over the control level with increasing doses of both X‐rays and fast neutrons. The relative biological effectiveness (RBE) of fast neutrons to X‐rays for MNC induction was estimated to be 4.3 ± 0.6. This value is close to the RBE value of 5.1 ± 0.3 reported for fast neutron induction of somatic crossing‐over mutations in Drosophila melanogaster that arise from recombination repair of DNA double‐strand breaks. These results and other data support our conclusion that the medaka gill cell micronucleus assay is a reliable short‐term test for detecting potential inducers of DNA double‐strand breaks. Environ. Mol. Mutagen. 44:108–112, 2004. © 2004 Wiley‐Liss, Inc.