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KMID : 0385020010170010009
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Korean Journal of Laboratory Animal Science
2001 Volume.17 No. 1 p.9 ~ p.15
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The RBE of Fast Neutrons versus Co γ-Rays for Apoptosis induction in mouse crypt cells
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Abstract
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These studies were performed to determine the relative biological effectiveness (RBE) of high linear energy transfer (LET) cyclotron fast neutrons (50 MeV) compared with low LET ^(60)Coγ-rays in the range of 0.25 to 1Gy for apoptosis induction in mice crypt cells. The numerical changes of apoptotic crypt cells were quantified by light microscopic analysis. RBE for apoptosis induction was studied at different doses after irradiation with the use of three different methods: morphological characterization of apoptotic crypt cells after DAPI and H&E staining.
The incidence of apoptotic cell death rose steeply at very low doses up to 1Gy, and radiation at all doses trigger rapid changes in crypt cells in stem cell region. These data suggest that apoptosis may play an important role in homeostasis of radiosensitive target organ by removing damaged cells. Dose-response curves obtained with both radiation qualities were revealed an initial steep increase in the number of apoptotic fragments below 1Gy, with a plateau of the curves at higher doses. The three different techniques used for analysis of apoptosis were similar results. The curve of dose-effect relationship for the data of apoptotic fragments was linear-quadratic in both radiation qualities, and a significant doseresponse relationship was found between the frequency of apoptotic cell and dose.
These data show a trend towards increase of the numbers of apoptotic crypt cells with increasing dose. Both the time course and the radiation dose-response curve for high and low LET radiation modalities were similar. The relative biological effectiveness (RBE) value for crypt cells was 2.072. Thus, the dose-response data confirm the high radiosensitivity of crypt cells and demonstrate that their response to undergo early interphase death by apoptosis is largely independent of LET.
Accordingly apoptosis induction of crypt cells could be used for determining quantitatively the biological responses to ionizing radiation in regard to the radiation protection and risk assessment, and biomonitering the intrinsic cellular radiosensitivity with neutron radiotherapy and screening test.
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