Dose-rate effect on transgenerational mutation frequencies in spermatogonial stem cells of the medaka fish.
The estimation of transgenerational genetic risk of radiation exposure to non-human species is crucial for the protection of ecosystems. Here we determined the frequency of specific-locus mutations at the five pigmentation loci in medaka spermatogonial stem cells after gamma irradiation at 0.03 cGy/min and 95 cGy/min. At each total dose, the mutation frequency was significantly lower in the 0.03-cGy/min group than in the 95-cGy/min group, suggesting a dose-rate effect. The ratio of the induced mutation frequency at 0.03 cGy/min to that at 95 cGy/min was approximately 0.42 from 0 to 1.9 Gy and approximately 0.33 from 1.9 to 4.75 cGy. In the mouse, this ratio is estimated to be 0.33 (Russell and Kelly, Proc. Natl. Acad. Sci. USA 79, 542-544, 1982). It is thus possible that the magnitude of the dose-rate effect on transgenerational mutation frequencies is comparable between mouse and medaka spermatogonia, suggesting similar dose-rate effects among vertebrates.
Shimada
Atsuko
A
Department of Biological Sciences, School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan. kirita@biol.s.u-tokyo.ac.jp
Eguchi
Hoshio
H
Yoshinaga
Shinji
S
Shima
Akihiro
A
D000818:Animals; D002478:Cells, Cultured; D002869:Chromosome Aberrations / Q000528:radiation effects*; D002875:Chromosomes / Q000528:radiation effects; D004252:DNA Mutational Analysis / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D005787:Gene Frequency / Q000528:radiation effects; D008297:Male; D051379:Mice; D009990:Oryzias / Q000235:genetics*; D011829:Radiation Dosage; D013045:Species Specificity; D013091:Spermatogenesis / Q000528:radiation effects*; D013234:Stem Cells / Q000528:radiation effects*