Induction of genomic instability after an acute whole-body exposure of mice to (5(6Fe ions

• Published in: Advances in space research Vol. 44; no. 8; pp. 895 - 906
• Main Authors: Rithidech, K N, Supanpaiboon, W, Honikel, L, Whorton, E B
• Format: Journal Article
• Language: English
• Published: 15-10-2009
• ISSN: 0273-1177
• DOI: 10.1016/j.asr.2009.05.001

The purpose of this study was to evaluate dose-response relationships for the in vivo induction of micronuclei (MN) as a measure of both initial radiation damage and the induction of genomic instability. These measurements were made in mouse blood erythrocytes as a function of radiation dose, radiation quality, time after irradiation, and the genetic background of exposed individuals. Blood samples were collected from two strains of mouse (CBA/CaJ and C57BL/6J) at different times up to 3 months following a whole-body exposure to various doses of 1GeV/amu (5(6Fe ions (0, 0.1, 0.5 and 1.0Gy, at the dose rate of a 1Gy/min) or (1(3(7)Cs gamma rays (0, 0.5, 1.0 and 3.0Gy, at the dose rate of 0.72Gy/min). Blood-smear slides were stained with acridine orange (AO). The frequencies of MN were measured in mature normochromatic-erythrocytes (MN-NCEs) and in immature polychromatic-erythrocytes (MN-PCEs). Effects of both types of radiation on erythropoiesis were also evaluated. As a measure of cell progression delay, a dose-dependent decrease in numbers of PCEs was observed at day 2 post-exposure in both strains, regardless of radiation quality. Subsequently, the levels of PCEs increased in all exposed mice, reaching control levels (or higher) by day 7 post-exposure. Further, at day 2 after the exposure, there was no increase in the frequency of MN-PCEs in CBA/CaJ mice exposed to (5(6Fe ions while the frequency of MN-PCEs elevated as a function of dose in the C57BL/6J mice. At day 4, there was no dose related increase in MN-NCEs in either strain of mouse exposed to (1(3(7)Cs gamma rays. Additionally, at the early sacrifice times (days 2 and 4), (5(6Fe ions were slightly more effective (per unit dose) in inducing MN-NCEs than (1(3(7)Cs gamma rays in CBA /CaJ mice. However, there was no increase in the frequency of MN-NCEs at late times after an acute exposure to either type of radiation. In contrast, both types of radiation induced increased MN-PCEs frequencies in irradiated CBA/CaJ mice, but not C57BL/6J mice, at late times post-exposure. This finding indicates the potential induction of genomic instability in hematopoietic cells of CBA/CaJ mice by both types of radiation. The finding also demonstrates the influence of genetic background on radiation-induced genomic instability in vivo.