Originally published in Acta Physiol. Scand. 30, 90 (1953). 



86. EFFECT OF IRRADIATION WITH X-RAYS ON THE 

 CATABOLISM OF METHYLALCOHOL IN THE MOUSE 



G. Hevesy 



From the Institute of Organic Chemistry and Biochemistry, University of Stockholm 



Watery suspensions of numerous enzymes can promptly be inacti- 

 vated, often by exposure to a restricted dose of ionizing radiation, as first 

 shown by Dale (1942). By exposing a suspension of adenosine triphos- 

 phatase (myosin) to a dose of only 10 r Barron (1949) observed a 10 per 

 cent inactivation of this enzyme. This type of prompt inactivation of 

 enzymes is not often met in vivo, possibly due to the presence of a great 

 variety of protecting substances and a rapid whipping out of possible 

 changes produced by the exposure. Forssberg (1945) did not succeed 

 in inactivating catalase present in the liver, even when he applied as- 

 massive doses as 83,000 r. A few days after exposure, a progressive in- 

 activation of catalase was, however, observed by Feinstein et aL 

 (1950) perhaps due to a blocking of the new-formation of metabolized 

 catalase molecules. The half-lifetime of catalase molecules in the liver 

 of the guinea pig was found to be 5 days (Bonnichsen and Theorell, 

 1951). 



Enzyme inactivation can also be studied by administering a metabolite- 

 marked w ith ^^C and studying the amount of labelled COg exhaled pre- 

 vious to and after exposure. If irradiation reduces the amount of labelled 

 CO2 exhaled, this does not prove an inactivation of the enzymes involved,' 

 viz. the effect of exposure may be due to other reasons than enzyme 

 inactivation and so far the latter took place, it may be difficult to 

 ascertain which of the enzymes involved in the catabolic process was 

 influenced. If, however, irradiation does not affect the amount of exhaled 

 COg we can conclude that the enzyme system involved in the catabolic 

 process was not influenced by exposure or, more correctly, that a suffi- 

 cient fraction of enzymes involved remained intact and can thus perform 

 its task at a normal rate. In the present note the results of a study of 

 the effect of exposure of mice to irradiation with X-rays on the cata- 

 bolism of methyl alcohol are communicated. 



