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1 February 2005 Characterization of Accelerated Iron-Ion-Induced Damage in Gap Junction-Competent and -Incompetent Thyroid Follicular Cells
L. M. Green, B. M. Bianski, D. K. Murray, S. S. Rightnar, G. A. Nelson
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Abstract

Green, L. M., Bianski, B. M., Murray, D. K., Rightnar, S. S. and Nelson, G. A. Characterization of Accelerated Iron-Ion-Induced Damage in Gap Junction-Competent and -Incompetent Thyroid Follicular Cells. Radiat. Res. 163, 172–182 (2005).

Early- and late-passage cultures of Fischer rat thyroid cells differ in their growth properties and gap junction competency. Previous studies comparing early- and late-passage cultures exposed to γ rays and proton beams revealed that differences in growth rate did not influence their responses; however, the presence of connexin 32 gap junctions conferred resistance to γ radiation. To further assess differences in radiation quality, suspension cultures of early- and late-passage cells were exposed to accelerated iron ions, and their comparative biological responses were measured. The iron-ion-irradiated cells displayed sustained levels of incorporated dUTP, reflecting persistent DNA damage. These results were supported by the frequency of chromosomal damage measured by micronucleus formation. Iron-ion irradiation induced micronuclei at a rate of eight per gray per 100 binucleated cells scored in early-passage cells and nine per gray per 100 binucleated cells scored in late-passage cells. Relative to photons, the calculated radiobiological effectiveness for frequency of micronuclei was 5.7 and 6.4 for the early- and late-passage cultures, respectively (P > 0.05). Levels of apoptosis fluctuated as a function of dose, and modest increases above basal levels persisted throughout the 48-h period. The comparison of retained follicular structures revealed differences in the α components of the linear-quadratic dose–response curves (0.60 Gy−1 for early-passage and 0.71 Gy−1 for late-passage cultures, P < 0.014). Cell cycle phase redistribution resulted in a G2 arrest (P < 0.001) for both early- and late-passage cultures. In conclusion, the response of thyroid follicular cells to high-LET radiation was not influenced by the presence of gap junctions or the proliferative status of the target cells.

L. M. Green, B. M. Bianski, D. K. Murray, S. S. Rightnar, and G. A. Nelson "Characterization of Accelerated Iron-Ion-Induced Damage in Gap Junction-Competent and -Incompetent Thyroid Follicular Cells," Radiation Research 163(2), 172-182, (1 February 2005). https://doi.org/10.1667/RR3297
Received: 19 February 2004; Accepted: 1 September 2004; Published: 1 February 2005
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