1996 Fiscal Year Final Research Report Summary
Experimental analysis of lung cancer induced by radon exposure and smoking
| Project/Area Number |
07458130
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
環境影響評価(含放射線生物学)
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| Research Institution | Shiga University of Medical Science |
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Principal Investigator |
IKEBUCHI Makoto School of Medicine, Shiga University of Medical Science, Research Associate, 医学部, 助手 (10121550)
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| Co-Investigator(Kenkyū-buntansha) |
KIMURA Hiroshi School of Medicine, Shiga University of Medical Science, Full Professor, 医学部, 教授 (00110560)
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| Project Period (FY) |
1995 – 1996
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| Keywords | radon / radon progeny / radon exposure system / rats / lung fibroblasts / micronuclei / biological effects / superoxide dismutase |
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| Research Abstract |
Experimental animal studies are thought to be useful for estimating risks of radon exposure. Such studies, however, had not done in Japan because of lack of radon exposure system. We developed a radon exposure system with 0.215 m^3 chamber in which 3 rats can be exposed. Radon concerntration measured by PICO-RAD system was fairly constant during exposure whereas the concentration of radon progeny monitored by filter-trapping method decreased. After exposure to radon, rats were sacrificed , and the frequency of micronuclei induced in lung fibroblasts was determined. The micronucleous frequency was related to the concentration of radon rather than that of radon progeny. When an average frequency of micronuclei (about 3%) was extrapolated to dose-response curves for X-ray induced micronuclei, the dose received by lung fibroblasts was found to correspond to 0.2-0.3 Gy of X-rays. The micronucleous frequency can be used as biological dosimeter. We tested for the activity of superoxide dismutase (SOD) in tissues using an electron spin resonance spectrometer. SOD activity was increased in kidney, liver and spleen after 4 h exposure, whereas it decreased after 16 h exposure, suggesting that this stimulating effect could last for a short time. The enhancement in SOD activity has been reported to occur after exposure to several Gy of X-rays. Compared with X-rays, the exposure of radon gave biological effects at lower absorbed doses. These findings would be helpful, when the experiments to determine the in vivo frequencies of cell transformation and 6-thioguanine resistant mutation are advanced for estimating risks of radon.
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