Internal doses in experimental mice and rats following exposure to neutron-activated 56 MnO 2 powder: results of an inte
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ORIGINAL ARTICLE
Internal doses in experimental mice and rats following exposure to neutron‑activated 56MnO2 powder: results of an international, multicenter study Valeriy Stepanenko1 · Andrey Kaprin2 · Sergey Ivanov1 · Peter Shegay2 · Kassym Zhumadilov3 · Aleksey Petukhov1 · Timofey Kolyzhenkov1 · Viktoria Bogacheva1 · Elena Zharova2 · Elena Iaskova1 · Nailya Chaizhunusova4 · Dariya Shabdarbayeva4 · Gaukhar Amantayeva4 · Arailym Baurzhan4 · Bakhyt Ruslanova4 · Zhaslan Abishev4 · Madina Apbassova4 · Ynkar Kairkhanova4 · Darkhan Uzbekov4 · Zaituna Khismetova4 · Yersin Zhunussov4 · Nariaki Fujimoto5 · Hitoshi Sato6 · Kazuko Shichijo7 · Masahiro Nakashima7 · Aya Sakaguchi8 · Shin Toyoda9 · Noriyuki Kawano10 · Megu Ohtaki5 · Keiko Otani10 · Satoru Endo11 · Masayoshi Yamamoto12 · Masaharu Hoshi10 Received: 21 March 2020 / Accepted: 31 August 2020 / Published online: 29 September 2020 © The Author(s) 2020
Abstract The experiment was performed in support of a Japanese initiative to investigate the biological effects of irradiation from residual neutron-activated radioactivity that resulted from the A-bombing. Radionuclide 56Mn (T1/2 = 2.58 h) is one of the main neutron-activated emitters during the first hours after neutron activation of soil dust particles. In our previous studies (2016–2017) related to irradiation of male Wistar rats after dispersion of 56MnO2 powder, the internal doses in rats were found to be very inhomogeneous: distribution of doses among different organs ranged from 1.3 Gy in small intestine to less than 0.0015 Gy in some of the other organs. Internal doses in the lungs ranged from 0.03 to 0.1 Gy. The essential pathological changes were found in lung tissue of rats despite a low level of irradiation. In the present study, the dosimetry investigations were extended: internal doses in experimental mice and rats were estimated for various activity levels of dispersed neutronactivated 56MnO2 powder. The following findings were noted: (a) internal radiation doses in mice were several times higher in comparison with rats under similar conditions of exposure to 56MnO2 powder. (b) When 2.74 × 108 Bq of 56MnO2 powder was dispersed over mice, doses of internal irradiation ranged from 0.81 to 4.5 Gy in the gastrointestinal tract (small intestine, stomach, large intestine), from 0.096 to 0.14 Gy in lungs, and doses in skin and eyes ranged from 0.29 to 0.42 Gy and from 0.12 to 0.16 Gy, respectively. Internal radiation doses in other organs of mice were much lower. (c) Internal radiation doses were significantly lower in organs of rats with the same activity of exposure to 56MnO2 powder (2.74 × 108 Bq): 0.09, 0.17, 0.29, and 0.025 Gy in stomach, small intestine, large intestine, and lungs, respectively. (d) Doses of internal irradiation in organs of rats and mice were two to four times higher when they were exposed to 8.0 × 108 Bq of 56MnO2 (in comparison with exposure to 2.74 × 108 Bq of 56MnO2). (e) Internal radiation doses in organs of mice were 7–14 times lower with the lowest 56MnO2 amount (8.0 × 107 Bq)
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