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| Year : 1994 | Volume
: 19
| Issue : 3 | Page : 108-117 |
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Biochemical Reasoning For Radiation Protection And Screening methods For Radiation Sensitivity And Potential Carcinogenicity
Emanuel Riklis, Richard B Setlow, Ingrid Emerit
Correspondence Address:
Emanuel Riklis
 Source of Support: None, Conflict of Interest: None  | Check |
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The problem of resistance or sensitivity to radiation, ionizing and non-ionizing alike, is of importance both to healthy individuals and to cancer patients. The possibility of severe sensitivity to radiation should be particularly recognized in the case of radiation workers and in patients undergoing radiotherapy. The sensitivity to ultraviolet light is of concern to the general public, but in particular to individuals who have a deficiency in their ability to repair damages in their DNA, a deficiency which is expressed in several diseases, in notably Xeroderma pigmentosum (XP), Ataxia telangiectasia (AT) and other autoimmune diseases. DNA repair capacity and the possiblity of affecting it by various modifying agents is a basic consideration in planning radiotherapy or phototherapy. The measurement of DNA repair capacity of cells, and the study of the effect of modifying agents on DNA repair is of importance. For these reasons, a relatively simple and accurate method for determining DNA repair has been developed, and it enables also to measure effects of modifying compounds on repair. The method is based on inhibition semiconservative DNA synthesis by treatment of cells with trimethylpsoralen + near UV light, and measuring repair synthesis as uptake of labelled thymidine after exposure to radiation. With this method an improved protection by the phosphoaminothiol WR-2721 was demonstrated, and shown to be a result of both reducing the damage and enhancement of DNA repair. Similar results were obtained with nicotinamide at low concentrations, acting in improving repair through the polyADPribose system. Recently, a clastogenic plasma factor which causes chromatid breaks in plasma cells has been found and isolated from plasma of individuals who have been exposed to radiation in the Chernobyl reactor accident. The breakage factor is known to exist also in plasma of individuals who suffer from a variety of autoimmune diseases, such as AT, Bloom's syndrome, polyarthritis and other inflammatory conditions. The clastogenic factor (CF) acts like a long-lived free radical, as it can be found years after the exposure to radiation, and may be eliminated by the antioxidant enzyme superoxide dismutase (SOD). This provides hope to individuals carrying the breakage factor, and this approach requires further research. The methods for measuring DNA repair capacity and the presence
of CF in irradiated persons are important contributions to the determination of risk of carcinogenesis. |
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