724 



ADVENTURES I?f RADIOISOTOPE RESEARCH 



Table la. — Foemation of Nucleic Acid in the Organs 

 OF 5 ^\'EEK Old Rats 



Table 16. — Formation of Nucleic Acid in the Organs of Starved Adult Rats 



As we have already stated, the ratio of the specific activity of the 

 nucleic acid P at the end of the experiment to the specific activity of 

 the free P at this same time is not a correct measure of the nucleic acid 

 molecules newly formed during the experiment. An accurate calculation 

 of this quantity requires a knowledge of the average specific activity 

 of the free P in the course of the experiment. With regard to the liver, 

 of course, these last mentioned quantities are very little different from 

 the values which have been obtained for unirradiated rats, as is shown 

 by the following data which we obtained on a previous occasion^-^\ 



The above figures prove that the average specific activity of the free 

 P in the 2 hr experiment is only about 5% less than the final activity. 

 The number 0.13 in the last horizontal line of Table 1 should, therefore, 

 be multiplied by 1.05 in order to arrive at the percentage rate of nucleic 

 acid formation in the liver in a period of 2 hr. Similar conditions are 

 involved in the kidneys, where the added phosphate ions likewise pene- 



1 H. EuLER and G. Hevesy Ark. Kern. 17A, No. 30 (1944). 



