Suppression of carcinogenic processes in mice by chronic low dose rate gamma-irradiation. (1st January 2003)

• Record Type: Journal Article
• Authors: Sakai, Kazuo; Hoshi, Yuko; Nomura, Takaharu; Oda, Takeshi; Iwasaki, Toshiyasu; Fujita, Kazuko; Yamada, Takeshi; Tanooka, Hiroshi
• Is Part Of: International journal of low radiation. Volume 1:Number 1(2003)
• Page Start: 142
• Page End: 146
• Publication Date: 2003-01-01
• Subjects: gamma irradiation -- low dose rate -- suppression of carcinogenesis -- skin tumour -- mouse; Radiobiology -- Periodicals; Radiation -- Health aspects -- Periodicals; Radiation tolerance -- Periodicals; 571.4505
• Languages: English
• ISSNs: 1477-6545

Abstract

Effects of low dose rate radiation on the process of carcinogenesis induced by a chemical carcinogen were examined. ICR female mice, 35 or 36 mice for each group, were kept and exposed to 137 Cs gamma-rays in the long-term low dose rate irradiation facility at the Central Research Institute of Electric Power Industry at a dose rate of 0.3, 0.96, or 2.5 mGy/h. Thirty-five days later, the mice were injected in the groin with 0.5 mg of 20-methylcholanthrene (MC) dissolved in olive oil, and irradiation was continued. Tumours started to appear 2 months after MC injection. Cumulative tumour incidences after 216 days following MC injection were 94% in the mice irradiated at 0.3 mGy/h, 76% at 0.95 mGy/h, 89% at 0.30 mGy/h, and 94% in non-irradiated control mice. The difference between the tumour incidence in the control mice and that in the mice irradiated at 0.95 mGy/h was statistically significant. These results indicate the suppressive effect of low dose rate irradiation on the process of tumour induction initiated by MC with an optimum dose rate of approximately 1 mGy/h.