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Effect of age on the sensitivity of the rat thyroid gland to ionizing radiation

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Title: Effect of age on the sensitivity of the rat thyroid gland to ionizing radiation
Authors: Matsuu-Matsuyama, Mutsumi / Shichijo, Kazuko / Okaichi, Kumio / Kurashige, Tomomi / Kondo, Hisayoshi / Miura, Shiro / Nakashima, Masahiro
Issue Date: May-2015
Publisher: 日本放射線影響学会 / Japan Radiation Research Society
Citation: Journal of Radiation Research, 56(3), pp.493-501; 2015
Abstract: Exposure to ionizing radiation during childhood is a well-known risk factor for thyroid cancer. Our study evaluated the effect of age on the radiosensitivity of rat thyroid glands. Four-week-old (4W), 7 -week-old (7W), and 8-month-old (8M) male Wistar rats were exposed to 8 Gy of whole-body X-ray irradiation. Thyroids were removed 3-72 h after irradiation, and non-irradiated thyroids served as controls. Ki67-positivity and p53 binding protein 1 (53BP1) focus formation (a DNA damage response) were evaluated via immunohistochemistry. Amounts of proteins involved in DNA damage response (p53, p53 phosphorylated at serine 15, p21), apoptosis (cleaved caspase-3), and autophagy (LC3, p62) were determined via western blotting. mRNA levels of 84 key autophagy-related genes were quantified using polymerase chain reaction arrays. Ki67-positive cells in 4W (with high proliferative activity) and 7W thyroids significantly decreased in number post-irradiation. The number of 53BP1 foci and amount of p53 phosphorylated at serine 15 increased 3 h after irradiation, regardless of age. No increase in apoptosis or in the levels of p53, p21 or cleaved caspase-3 was detected for any ages. Levels of LC3-II and p62 increased in irradiated 4W but not 8M thyroids, whereas expression of several autophagy-related genes was higher in 4W than 8M irradiated thyroids. Irradiation increased the expression of genes encoding pro-apoptotic proteins in both 4W and 8M thyroids. In summary, no apoptosis or p53 accumulation was noted, despite the expression of some pro-apoptotic genes in immature and adult thyroids. Irradiation induced autophagy in immature, but not in adult, rat thyroids.
Keywords: Apoptosis / Autophagy / p53 binding protein 1 / Rat / Thyroid / X-ray
URI: http://hdl.handle.net/10069/35499
ISSN: 04493060
DOI: 10.1093/jrr/rrv003
Rights: © The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology. / This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Type: Journal Article
Text Version: publisher
Appears in Collections:Articles in academic journal

Citable URI : http://hdl.handle.net/10069/35499

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