1990, The British Journal of Radiology, 63, 81-82

Correspondence (The Editors do not hold themselves responsible for opinions expressed by correspondents) Chemical protectors: their potential application against occupational radiation hazards THE EDITOR—SIR,

The last two decades have seen a tremendous effort to find suitable chemicals that can be used for normal-tissue protection in tumour radiotherapy. The most promising compound so far is the synthetic phosphorothioate derivative of cysteamine (WR-2721), studied extensively for its protective effect in mammals and man (Yuhas, 1980). The initial enthusiasm was dampened by the discovery that repeated injections of this drug in man produced undesirable toxic side effects (Utley et al, 1976; Turrisi et al, 1983), as well as by the controversy regarding the preferential protection of normal tissues by the drug (Denekamp et al, 1983). According to Denekamp and Rojas (1987), WR-2721 is unlikely to become a widely used adjunct to conventional radiotherapy. Another drug, 2-mercaptopropionylglycine (MPG), caught the attention of scientists because of its non-toxic nature and its effectiveness after oral administration, but its low level of protection makes it a less attractive candidate for use in clinical radiotherapy (Sugahara et al, 1970). Many recent studies have therefore concentrated on methods to reduce the toxicity of WR-2721 and on finding alternative drugs which are more potent and less toxic. However, no suitable chemical protector is available so far that can be routinely used in clinical practice. One area where SH protectors can be of practical application appears to be in the field of health physics, where workers are exposed to the risk of occupational radiation hazards. The radiation workers receive a level of exposure higher than background in the course of their work, and sometimes minor accidents or work related to maintenance and repair of nuclear facilities will increase the exposure levels, with a consequent increase in the risk to the person. The main effect from such exposure is a change in chromosomes which can lead to later complications, including cancer and genetic effects, which will be manifested in subsequent generatioins (UNSCEAR, 1982). Pregnant women face a higher risk because of the high susceptibility of developing embryos to very small doses of radiation, amounting to only a few cGy. Experiments on mice exposed to sublethal doses of y radiation ranging from 50cGy to 600 cGy, using WR-2721 Table I. Protective effect of the drugs on the bone marrow chromosomes of Swiss albino mice whole body exposed to 4.5 Gy y radiation, observed on Day 1 post-irradiation Treatment" Control WR-2721

Drug dose (mg/kg) 300 150

MPG WR-2721 + MPG

Vol. 63, No. 745

20 150 + 20

Normal metaphases (%) 44.17 + 0.92 77.66+1.11 p< 0.001 69.33 + 1.17 p< 0.001 58.50 + 0.86 />

Chemical protectors: their potential application against occupational radiation hazards.

1990, The British Journal of Radiology, 63, 81-82 Correspondence (The Editors do not hold themselves responsible for opinions expressed by correspond...
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