Micronuclei induced by low dose rate irradiation in early spermatids of p53 null and wild mice.
To obtain evidence of the dose-rate effect on induction of micronuclei in early spermatids, we observed frequencies in wild-type p53(+/+), heterozygous p53(+/-) and null p53(-/-) mice 14 days after gamma rays irradiation at a high (1,020 mGy/min) or a low (1.2 mGy/min) dose-rate. A dose- and dose-rate-related increase in micronuclei was seen in early spermatids with no difference between the different p53 status. These data were found to be best fitted by a linear-quadratic dose-response model at a high dose-rate, and by a linear dose-response model at a low dose-rate. The yields at 1.2 mGy/min were significantly lower than those at 1,020 mGy/min in the same manner, independent of p53 status. Testis weight declined significantly after 3 Gy irradiation, but did not depend on dose-rates. In our other studies, we observed the complete elimination both of malformation in fetuses and CD3- 4+ mutant T-lymphocytes in p53(+/+) mice, but not in p53(-/-) mice after irradiation. This indicates that concerted DNA repair and p53-dependent apoptosis are likely to completely eliminate mutagenic damage from the irradiated tissues at low doses or dose-rates in teratogenesis and lymphocytes. In the germ cell, however, irradiation at 1.2 mGy/min was mutagenic, independent of p53 status.
Kunugita
Naoki
N
Department of Health Information Science, University of Occupational & Environmental Health, Yahatanishi-ku, Kitakyushu 807-8555, Japan. kunugita@med.uoeh-u.ac.jp
Kakihara
Hiroyo
H
Kawamoto
Toshihiro
T
Norimura
Toshiyuki
T
D000818:Animals; D002467:Cell Nucleus / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D013087:Spermatids / Q000528:radiation effects*; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
D016159:Tumor Suppressor Protein p53