308 RADIATION BIOLOGY 



ionic yield (Table 5-1) upon oxidation by ionizing radiations is proof for 

 this contention. Furthermore, there is in some living cells an enzyme, 

 glutathione reductase, which reduces one of these thiols (glutathione), 

 bringing it back to its active state (Conn and Vennesland, 1951). 



Protection of enzymes with glutathione was reported by Barron 

 (1946b), who at that time advocated the use of thiols as protection against 

 the effects of ionizing radiations. Not only sulfhydryl enzymes are pro- 

 tected, but jionsulfhydryl enzymes as well (Holmes, 1950). The prac- 

 tical application was reported by Patt et al. (1949) and by Chapman et al. 

 (1949), who protected rats against lethal doses of X radiation by previous 

 injection of cysteine or glutathione. 



A simple test for predicting the protective power would be to measure 

 the ionic yield of the substance on irradiation and its rate of autoxidation, 

 since the products in these cases may be regarded as substances akin to 

 antioxidants. 



The experiments with sulfhydryl enzymes have shown that thiol com- 

 pounds can also produce reactivation of the irradiated enzyme. How- 

 ever, oxidation of other oxidizable groups of protein molecules is not 

 reversed by thiols, and in such cases other agents have to be looked for. 

 Thiol compounds may protect from the indirect action of ionizing radia- 

 tion and may reactivate sulfhydryl enzymes inhibited by irradiation, but 

 they cannot be effective therapeutic agents. 



If protein denaturation has occurred, there is no course left (since this 

 is an irreversible reaction) but to provide the organism with means for an 

 accelerated rate of protein synthesis. 



It 



REFERENCES 



(Information regarding government documents indicated by an asterisk may be 

 obtained from the Office of Technical Services, Department of Commerce, 



Washington, D.C.) 



Abrams, R. (1951) Effect of X rays on nucleic acid and protein synthesis. Arch. 



Biochem., 30: 90-99. 

 Ahlstrom, L., H. v. Euler, and G. Hevesy (1945) Uber die indirekte Wirkung von 



Rontgenstrahlen auf das Jensensarkom. Arkiv Kemi, Mineral. Geol. A19 (13): 



1-16. 

 ■ , , , and K. Zerahn (1946) Attempts to find products blocking 



nucleic acid formation in the circulation of an irradiated organism. Arkiv Kemi, 



Mineral. Geol., A23 (10): 1-6. 

 Albers, D. (1940) Die Beeinflusung der Serumphosphatase durch Ultra violette-licht 



und Rontgenstrahlen. Fundamenta Radiologica, 5: 157-164. 

 Anderson, R. S., and B. Harrison (1943-44) The quantitative effect of X-rays on 



ascorbic acid in simple solutions and in mixtures of naturally occurring com- 

 pounds. J. Gen. Physiol., 27: 69-73. 

 Barron, E. S. G. (1946a) Effect of X rays on tissue metabolism. USAEC Report 



CH-3654.* 



