RENEWAL OF ACID SOLUBLE I'HOSPHORUS COMPOUNDS IX ORGANS OF RABBIT 371 



that the rate of new formation^i^ of hexosemonopliosphate is correspond- 

 ingly larger in the kidney. The incorporation of labelled P atoms into 

 the hexosemonophosphate molecules must be preceded by a penetra- 

 tion of the labelled inorganics P into the cells of the organ. ]f this 

 process is slow, the rate of formation of labelled hexosemonophosphate 

 molecules is bound to be comparatively slow, in spite of a possibly 

 very fast rate of new formation of the hexosemonophosphate molecules 

 inside the cells of the organ in question. In fact, the labelled inorganic 

 phosphate molecules penetrate very much faster into the kidney cells 

 than into the muscle cells. To get proper information on the rate of 

 renewal of an organic compound in an organ, we have to compare the 

 specific activity of the P isolated from the organic compound in question 

 at the end of the experiment with the average value of the specific activ- 

 ity of the cellular inorganic P prevailing during the experiment. The 



Table 1. — Extent of Rexewal of the Total Organic Aciu .Soluble P in the 



Organs of the Rabbit 



Rabbit II. Weight 2.6 kgm. 

 Inti'avenous injection during 215 min 



(') The inorganic P extracted from the heart contains partly such inorganic P atoms which were formed 

 through decomposition of creatinephosphoric acid prior to the extraction. As the specific activity of the 

 creatine P is, after the lapse of i hours, lower than that of the inorganic P (comp. the muscle values in Table 

 3!), the specific activity of the cellular inorganic P of the heart is in fact higher than that stated above 

 and, correspondingly, the values of the rate of renewal of the organic acid soluble P compounds in the lieart 

 are smaller than those stated in the last and the last but one column of Table 1. 



^1^ The significance of the notion of the rate of now formation is discussed in 

 the paper by G. Hevesy and L. Hahn, Kgl. Danske Vidensk. Selskab, Biol. Medd. 

 15,5(1940). 



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