NUCLEIC ACID IX THE ORGANS OF THE RAT 



667 



The specific activity of the creatine phosphoric acid was determined 

 in the following way. After the removal of the free P as ammonium 

 magnesium salt, the filtrate was slightly acidified and heated for a very 

 short time. The free P obtained by the decomposition of creatine phos- 

 phoric acid was then again precipitated as ammonium magnesium salt. 

 While, after the lapse of one day or more, the specific activity of the 

 creatine phosphoric acid phosphorus was found to be just as high as 

 the specific activity of the "free" P present in the muscle tissue, after 

 the lapse of 2 hours the ratio of the specific activities was found to be 

 only 0.6- 



SPECIFIC ACTIVITY OF THE NUCLEIC ACID EXTRACTED FROM 



DIFFERENT ORGANS 



The results of the determination of the specific activity of the nucleic 

 acid phosphorus extracted from the different organs is seen in Table 2. 

 I and II denote the values obtained in the first and second experiments 

 respectively. In each experiment the organs of 8 rats were pooled. The 

 values shown in the last column indicate the percentage ratio of the 

 specific activity of the nucleic acid P and the specific activity of the 

 "free" phosphate P of the different organs. 



Table 2. — Specific Activity(i) of the Nucleic Acid Phosphorus 



Extracted from Different Organs of 8 Rats 4 Days after the 



Administration of Labelled Phosphate X 1000 



Organ 



Specific activity x 1000 



11. 



Percentage ratio of the 



specific activity of nucleic 



acid P and free P 



(Percentage renewal)'-' 



Small intestinal mucosa 



Spleen 



Muscle 



Liver 



Testes 



Kidney 



Brain 



59 

 23 



8.8 

 4.2 

 10 

 2.1 

 2.3 



(1) Percentage of the '"P administered present in 1 mgm P. 



''> When calculating the above ratio, we must take into account that the nucleic acid has been extracted 

 from the organs of 8 rats. 



When calculating the figures of the last column, we have not taken the 

 figures of the specific activity of the free phosphate P as stated in Table 1, 

 but corrected these for the presence of labelled P in the extracellular space 

 of the organs. The extracellular P is not utilized to build up nucleic acid, 

 and we have to consider the ratio of the specific activity of the nucleic 



