68 



NEUTRON EFFECTS ON ANIMALS 



The summarized data show that the serum phosphatase activity of rats 

 irradiated under these conditions undergoes a decrease which is at a max- 

 imum near the fourth day after exposure and which, at that time, amounts 

 to approximately 75 per cent of the normal level. The average values for 

 the various groups indicate a subsequent increase to near-normal values 

 by the seventh day; on the twentieth day levels somewhat lower than 

 normal are found. 



In connection with this observed decrease in enzyme activity, several 

 additional determinations have been carried out. Serum samples were 

 made by mixing normal rat serum (high activity) with serum from rats 

 previously irradiated (low activity) in various proportions. Since the 

 phosphatase values found for the mixtures were always essentially equal 



TABLE I 



The Effect of Neutron Radiation on Serum Alkaline Phosphatase Activity in Female 



Rats 



* Irradiation dose: 56 n. The period of irradiation was approximately one hour. 

 t One-hour units per 100 cc. serum (9). 



to those calculated on an additive basis, there is no indication that the 

 decrease found after irradiation is due to the presence of inhibitors or to a 

 lack of activating agents. 



This decrea.se, in the light of the observation made by Ross and Ely (10) 

 that the food intake of rats irradiated under similar conditions is greatly 

 diminished, appears to resemble that observed by Weil and Russell (11) 

 and by Gould (12) in rats which were fasted for one or more days. The 

 decrease in serum alkaline phosphatase after fasting has been confirmed 

 in this study; a group of ten rats was fasted for 24 hours, after which time 

 the average enzyme activity was found to be 29.9 units. This value 

 corresponds to a decrease of approximately 70 per cent based on that found 

 for the normal group. 



