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ADVENTURES IN RADIOISOTOPE RESEARCH 



Table 6. — Specific Activity of the Cellular Inorganic P and Phosphatide 



P Extracted from the Organs 



Rabbit V. — Weight: 2.1 kgm 

 Intravenou.s injection during 2.50 min 



(•) Turnover rate calculated on the assumption that the formation of phosphatides took place with 

 incorporation of cellular inorganic P. 



(-) Turnover rate calculated on the assumption that the formation of phosphatides took place with 

 incorporation of extracellular inoi'ganic P. 



Table 7. — Specific Activity of the Celli'lar Inorganic P and Phosphatide 



P Extracted from the Organs 



Rabbit VI. — Weight: 2.6 kgm 

 Subcutaneous injection during 255 min 



<') Turnover rate calculated on the assumption that the formation of phosphatides took place with 

 incorporation of cellular inorganic P. 



C') Turnover rate calculated on the assumption that the formation of phosphatides took place with 

 incorporation of extracellular inorganic P. 



of water can be led from one pond into the other by a narrow channel; 

 salt water, however, (salt corresponding to labelled phosphatides in 

 our case) cannot pass the channel without the water of the channel 

 becoming salt as well. The concept of "specific activity" proves, thus, 

 to be of great use when putting forward considerations such as those 

 discussed above. 



One may say, in respect of these considerations, that, while the specific 

 activity of the average plasma phosphatides is low, one of the phos- 

 phatide fractions (phosphatides represent a mixture of numerous com- 

 pounds) might be synthesised at a very fast rate in the intestinal mucosa, 

 and the labelled molecules formed in this process might have rushed 

 through th(> plasma at a last rale inio Ihe liver without raising much 



