HZE RADIATION EFFECT FOR HEREDITARY RETINAL CARCINOMAS

Cancer is a heritable disorder of somatic cells. The Eker rat is well characterized as an animal model for dominantly inherited cancer. All of the Eker rats develop renal carcinomas (RC) approximately 1 year after birth. According to Mendelian laws of inheritance, this occurrence suggests the existence of a single responsible gene. Tuberous sclerosis complex (Tsc2) gene encoding a tumor suppressor protein, are the responsible factor for the RC. We have investigated the effects of space radiation on carcinogenesis and analyzed RBE ratio of tumor induction, in which we compared the effects of heavy-ion (C-290MeV/u,Fe-500MeV/u) exposure and X-ray exposure. Pregnant rats were irradiated by carbon-ions, iron-ions and X-rays by 0.5Gy, 1Gy, 2Gy and 3Gy individually on 19th day of gestation. These rats were sacrificed at age of 8 weeks, and organ weight and tumor genesis were measured. Thymus, Lung, Liver, Spleen weight were not different at 1Gy, but decreased by 50% at 3Gy irradiation. Kidney, Brain, Testis were radiation sensitive organs of which weight were decreased by 40% at 1Gy and by 80% at 3Gy. The number of hereditary renal carcinomas per one cross section of kidney were 3.7(1Gy), 42.0(3Gy) in the case of X-ray exposure, and 4. (1Gy) and 54.1(3Gy) by carbon ion exposure, and 14.5(1Gy) and 49.6(2Gy) by iron ion exposure. The Dose-response relationship on radiation-induced carcinoma was clearly fitted by LQ model. The RBE were observed as 1.1 for carbon-ions, and 1.6 for iron ions.3rd International Workshop on Space Radiation Resarchconference objec