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Updated: Aug 12, 2026

One-step Protocol for Evaluation of the Mode of Radiation-induced Clonogenic Cell Death by Fluorescence Microscopy
Published on: October 23, 2017
Threshold effect for teratogenic risk of radiation depends on dose-rate and p53-dependent apoptosis
F Kato1, A Ootsuyama, S Nomoto
1Department of Radiation Biology & Health, School of Medicine, University of Occupational & Environmental Health, Kitakyushu, Japan. fumiok@med.uoeh-u.ac.jp
Purpose:
To obtain evidence that the p53 gene is indispensable for reduction of high teratogenic risk of radiation at a high dose-rate to zero risk by lowering the dose-rate.
Materials And Methods:
Wild-type p53(+/+), heterozygous p53(+/-) and null p53(-/-) mice were exposed to gamma-rays at high or low dose-rates during days 9.5-10.5 of gestation. The incidence of malformations and prenatal deaths was studied. Frequencies of cells dying by apoptosis were measured during or after protracted irradiation.
Results:
After irradiation with 2 Gy, the frequency of apoptotic cells increased to 20% for p53(+/+) mice and did not increase at all for p53(-/-) mice. For p53(+/+) mice, 2 Gy y-rays induced 70% malformations when given at 1.06 Gy/min, but no malformations above the control when given at 1.2 mGy/min. In contrast, after irradiation of p53(-/-) foetuses with 2 Gy at 1.2mGy/min, the incidence of malformations increased 12% above control levels.
Conclusion:
Foetal irradiation with 2 Gy at 1.2 mGy/min was not teratogenic for p53(+/+) mice but teratogenic for p53(-/-) mice. This indicates that the p53 gene is indispensable for a threshold effect in the risk of radiation at low doses or dose-rates.
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