chemical compounds used to protect living organisms—microorganisms, plants, animals, and man—from ionizing radiation. Radioprotectors are introduced into the environment or directly into the organism before or during irradiation. Effective radioprotectors include compounds containing sulfhydryl (thiol) groups (—SH), such as cysteine, mercaptoamines and indolylalkylamines. Radioprotectors generally diminish the consequences of irradiation, that is, its fatal and nonfatal effects, including genetic effects. They also reduce the intracellular or interstitial oxygen pressure and increase the amount of endogenous thiols, which is accompanied by a decrease in the oxidation-reduction potential.

The effectiveness of radioprotectors is expressed by a dose reduction factor, which is equal to the ratio of radiation doses producing identical effects in the presence or absence of radioprotectors. The dose reduction factor depends on the conditions of the irradiation and the physical properties of the radiation: with irradiation during a state of hypoxia, the factor is less than with irradiation in the presence of oxygen. The factor is less during radiation with high linear energy transfer (α particles, neutrons, and heavy ions) than during radiation with low linear energy transfer (X rays and γ rays). The effect of radioprotectors also depends on the properties of the organism. Thus, some radioprotectors may protect microorganisms and cells in a culture and not protect mammals.


Bacq, Z. M. Khimicheskaia zashchita ot ioniziruiushchei radiatsii. Moscow, 1968. (Translated from English.)
Romantsev, E. F. Radiatsiia i khimicheskaia zashchita [2nd ed.]. Moscow, 1968.
Graevskii, E. Ia. Sui’fgidril’nye gruppy i radiochuvstvitel’nost’. Moscow, 1969.
Sumarukov, G. V. Okislitel’noe ravnovesie i radiochuvstvitel’nost’ organizmov. Moscow, 1970.


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Therefore, agents which can protect cellular membranes against IR and ROS/RNS will have potential benefits as radioprotectors, antioxidant and antimutagens (Odin 1997; Stavric 1994).
While its role as a therapy to reduce side effects of radiation on humans is ongoing, recent studies have shown that dietary supplements containing lipoic acid can act as radioprotectors in mice.
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is a Radiation Oncologist and Professor at the University of Wisconsin Medical School, with dual appointments in the Departments of Human Oncology and Neurological Surgery with interests in neuro-oncology, IMRT, IGRT, radiosensitizers, radioprotectors, CNS tumors, lung cancer, pediatric radiation oncology, and advanced imaging.
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Interference with endogenous radioprotectors as a method of radiosensitization in "IAEA's Modification of Radiosensitivity of Biological Systems.
1:00 pm - 5:00 pm - Poster Session Radiosensitizers and Radioprotectors
55, (56) Tocotrienols are known to combat reactive oxygen species (ROS) and reactive nitrogen species (RNS), the primary source of radiation-induced damage; and the fact that tocotrienols have potent antioxidant properties lends support to AFFRI's original hypothesis--"strong antioxidants make strong radioprotectors.
Positive results obtained on gamma-irradiated mice given EEP and quercetin, complementary with our earlier observations on survival of irradiated mice, indicate that these compounds could be considered effective non-toxic radioprotectors.