Originally published in Nature, 168, 692 (1951). 



83. EFFECT OF IRRADIATION BY X-RAYS ON THE 

 EXHALATION OF CARBON DIOXIDE BY THE MOUSE 



G. Hevesy and A. Forssberg 

 From the Institute for Research in Organic Chemistry and Institute of Radio- 

 physics. Stockholm 



It has been shown previously that the rate of formation of deoxyribo- 

 nucleic acid is depressed by a sublethal dose of X-rays. Both the incor- 

 poration of phosphorus-32^^~^^ and that of carbon- 14^^' ^^ was found to be 

 reduced about 50 per cent. The rate of incorporation of carbon-14 into 

 the purines of ribonucleic acid is reduced as well^'\ though to a smaller 

 extent than its incorporation into the purines of deoxyribonucleic acid. 

 These blocking effects are presumably partly due to inactivation of 

 enzymes involved in the synthesis of the deoxyribonucleic acid and 

 ribonucleic acid compounds. One or a few days after irradiation, the 

 incorporation of carbon-14 into purines of deoxyribonucleic acid has 

 almost returned to the rate for the non-irradiated controls. This sug- 

 gests that a partial reactivation has occurred. The early metabolic 

 changes produced by irradiation are not confined to interference with 

 nucleic acid synthesis. We find that irradiation interferes with glucose 

 metabolism as well. 



Fully grown mice which had been fed ad libitum were placed in per- 

 forated metal boxes which prevented gross movement. In each experi- 

 ment four such boxes were symmetrically placed in a metal cylinder 

 containing carbon dioxide-free air and kept at 27^. Exhaled carbon 

 dioxide was swept from the brass cylinder by carbon dioxide-free air at 

 constant velocity and collected in a series of three wash-bottles contain- 

 ing barium hydroxide. At intervals of 10 min the air stream was switched 

 over to another aggregate of wash-bottles. The carbon dioxide was 

 collected for one hour. 



Glucose (60 fig having an activity of 0.03/u(\) labelled in all its carbon 

 atoms was injected subcutaneously into each mouse immediately after 

 irradiation. Collection of carbon dioxide started 8 min after injection. 

 The increase in weight of barium carbonate with increasing time shown 

 in the graph has no significance, as it is a result of the fact that the 

 content of exhaled carbon dioxide in the metal cylinder increases with 

 time. We wished only to determine the ratio of carbon dioxide exhaled 

 by irradiated and control mice, not the total amount exhaled. 



