Originally published in Ark. Kern. 19A, No. 9 (1944). 



72. THE EFFECT OF X-RAYS ON NUCLEIC ACID 

 FORMATION IN THE ORGANS OF THE RAT 



LrciE jAhisteom, Hans Euler and George Hevesy 



From the Institute for Research in Organic Chemistry, Stockholm 



On an earlier occasion^^^ we found that the synthesis of desoxyribonucleic 

 acid molecules in the Jensen-sarcoma of the rat is inhibited by the action 

 of X-rays. We have extended our studies to the effect of radiation on 

 the metabolism of nucleic acid in the normal organs of the rat and we 

 describe the outcome of these experiments in the following pages. 



EXPERIMENTAL 



Albino rats with ages between 3 days and 12 months were available 

 for this work. In order to obtain sufficient amounts of nucleic acid it 

 w^as necessary simultaneously to work with organs of several animals, 

 because the requisite detailed purification of nucleic acid from other 

 phosphorus-containing compounds is accompanied by considerable 

 losses of material. As we described previously^i^ the nucleic acid was 

 purified with hydrochloric acid and methanol, three times with the 

 addition of phosphate and then twice more without. One-fifth of the 

 nucleic acid obtained was used for measuring the radioactivity and 

 another fifth for colorimetric determination of phosphorus. 



The radioactive phosphate was administered to the rats by sub- 

 cutaneous injection at the beginning of the experiment, using 0.1 cm^ 

 of a physiological saline solution which contained some active sodium 

 phosphate. The dose administered to one rat had an activity of from 

 3 to 6 //c. The animals were killed two hours after injection. 



The irradiated animals were given the injection immediately after 

 irradiation. The irradiation dose varied between 1300 and 3000 r. The 

 X-ray tube was operated at a voltage of 165 kV. A 0.5 mm copper foil 

 and 1 mm aluminium foil were used as radiation filters. The field size 

 was 10X10 cm2. 



1. H. Euler and G. IIevesy, Kgl. Danske Vidensk. Selskab. Biol. Medd. 17, 

 No. 8 (1942); Ark. Kern. 17A, No. 30 (1944). 



46 Hevesy 



