• The Korean Journal of Nuclear Medicine
• /
• v.27 no.1
• /
• pp.112-117
• /
• 1993

Background Radioiodine ($^{131}I$), a major component of nuclear fallout and a valuable therapeutic agent for thyrotoxicosis and thyroid cancer, has been regarded as a mutagen or a carcinogen without any convincing evidence. To evaluate the genotoxicity of radioiodine ($^{131}I$) we performed a micronuclei test in mice bone marrow. Materials and methods : Mice (ICR strain, $25{\sim}30 g$) were divided to 4 groups: control, group 1 (0.17 mCi/kg, usual therapeutic dose for thyrotoxicosis), group 2 (1.67 mCi/kg, usual therapeutic dose for thyroid cancer), and group 3 (16.67 mCi/kg, usual accumulated dose causing bone marrow suppression). $^{131}I$ was administered intraperitoneally. Ten mice of each group were sacrificed at days 1 and 3. Bone marrow were smeared and stained with May-Grunwald Giemsa method. One thou-sand polychromatic erythrocytes (PCE) and normochromatic erythrocytes (NCE) were counted under the light microscope, and the number of micronucleated PCEs were recorded. Results : The frequency of micronuclei in PCE (and NCE in parenthesis) in the control group was $0.25{\pm}0.07$ ($0.23{\pm}0.07$)% in day 1 and $0.24{\pm}0.07$ ($0.21{\pm}0.07$)% in day 3. Those in group 1 was $0.27{\pm}0.1$ ($0.23{\pm}0.09$)% in day 1 and $0.28{\pm}0.07$ ($0.25{\pm}0.06$)% in day 3. Micronuclei was noted in $0.29{\pm}0.08$ ($0.26{\pm}0.09$)% in day 1 and $0.31{\pm}0.05$ ($0.29{\pm}0.06$)% in day 3 in group 2, and in $0.32{\pm}0.06$ ($0.25{\pm}0.09$)% in day 1 and $0.33{\pm}0.08$ ($0.3{\pm}0.06$)% in day 3 in group 3. There was no difference in the frequency of micronuclei between each groups (p> 0.05). Conclusion : Radioiodine ($^{131}I$) did not cause any genotoxicity in mice bone marrow even at the large dose (16.67 mCi/kg).

• Radiation Oncology Journal
• /
• v.11 no.1
• /
• pp.35-42
• /
• 1993

The dose response of the number of micronuclei in cytokinesis-blocked (CB) lymphocytes after in vitro irradiation with $\gamma$-rays and neutrons in the 5 dose ranges was studied for a heterogeneous population of 4 donors. One thousand binucleated cells were systematically scored for micronuclei. Measurements performed after irradiation showed a dose-dependent increase in micronuclei (MN) frequency in each of the donors studied. The dose-response curves were analyzed by a linear-quadratic model, frequencies per 1000 CB cells were ($0.31{\pm}0.049$)D+($0.0022{\pm}0.0002)D^2+(13.19{\pm}1.854) (r^2=1.000,\;X^2=0.7074,\;p=0.95$) following $\gamma$ irradiation, and ($0.99{\pm}0.528$)\;D+(0.0093{\pm}0.0047)\;D^2+(13.31{\pm}7.309)\;(r^2=0.996,\;X^2=7.6834,\;p=0.11) following neutrons irradiation (D is irradiation dose in cGy). The relative biological effectiveness (RBE) of neutrons compared with $\gamma$-rays was estimated by best fitting linear-quadratic model. In the micronuclei frequency between 0.05 and 0.8 per cell, the RBE of neutrons was $2.37{\pm}0.17$. Since the MN assay is simple and rapid, it may be a good tool for evaluating the $\gamma$-ray and neutron response.