108 HOLLAENDER, StAPLETON AND BuRNETT 



Bonet-Maury and Lefort, 1948; Weiss, 1944, 1946; Fricke, 

 1935; Dainton, 1948; Lea, 1947). The influence of X-rays on 

 certain organic chemicals and enzymes is now being studied 

 in many laboratories. Very little is known of the interaction 

 of the products of radiation with macromolecules and struc- 

 tures like chromosomes, mitochondria, etc., in the living cells. 



One explanation for the effect of sulphydryl compounds is 

 that they compete with or replace the sulphydryl groups of 

 certain enzymes which are very sensitive to X-rays. This 

 has support in Barron's (1949) work, where the special 

 sensitivity of sulphydryl-containing enzymes has been 

 emphasized. There seems to be little doubt that sodium 

 hydrosulphite protects by its ability to tie up oxygen. In 

 addition, it may possibly remove oxygen from inside the cells. 

 The protective ability of alcohol may be partly due to the 

 fact that, at high concentration, it can tie up oxygen. After 

 incubation at low concentration it may entet the metabolic 

 cycle where, in the course of oxidation, a considerable amount of 

 oxygen may be utilized. The possibility exists that metabolic 

 compounds may replace basic cell constituents destroyed by ir- 

 radiation. The utilization of formate in nucleic acid synthesis 

 may explain in part the protective action of this compound. 



Moreover, the excellent protection afforded by carboxylic 

 acids, w^hen incubated with cells prior to irradiation, suggests 

 also the possibility that these compounds may supply some 

 essential intermediate or overcome a block in the carboxylic 

 acid cycle induced by ionizing radiations. Interference with 

 some step in the Krebs citric acid cycle, brought about by 

 X-rays, is indicated in the report by DuBois, Cochran, and 

 Doull (1951). This suggests the use of some of these com- 

 pounds as protective agents against ionizing radiation damage 

 in mammals. Some aspects of this problem are now being 

 investigated in our laboratory. 



REFERENCES 



Allen, A. O. (1948). J. phys. Colloid Chem., 52, 479. 

 Anderson, E. H. (1951). Proc. nat. Acad. Sci., Wash., 37, 340. 

 Bacq, Z. M. (1951). Experientia, 7, 11. 



