320 



ADVENTURES IN RADIOISOTOPE RESEARCH 



to that of a few molecular layers. It is, therefore, quite conceivable 

 that in the outer layer of the stroma a slow rejuvenation of the phos- 

 phatide molecules takes place with incorporation of plasma P. In the 

 case of finding an organic P fraction extracted from the cells or the 

 corpuscles to show a higher specific activity than the cellular, respecti- 

 vely corpus cular inorganic P, we would be justified to conclude that the 

 synthesis of the organic compound in question did not take place inside 

 the cells, respectively the corpuscles. Investigations in the above men- 

 tioned direction may bring forward results of histochemical interest. 



RESULTS OF EXPERIMENTS 



Investigation of the total petrol-ether soluble phosphatide mixture 

 Experiments with rabbits 



Table 3. — Spkcific Activity of the Cellular Inorganic P and Phosphatide 



P Extracted from the Organs 



Rabbit II. — Weight: 2.6 kgm 

 Intravenous injection during 215 min 



<'> Calculated on the assumption that the formation of phosphatides took place with incorporation of 

 fellular inorganic P. 



(''' Calculated on the assumption that the formation of phosphatides took place with incorporation of 

 extracellular inorganic P. 



(=' In several experiments the specific activity of the marrow inorganic P was found to be surprisingly 

 low. even lower than that of the ester P. These low values were presumably due to the presence of traces 

 of only slightly active bone P in tlie marrow sample. 



Critical remarks 



In Tables 2 — 9, data were given for the turnover rate of phosphatides 

 in different organs of the rabbit. When calculating those values we 

 assumed that the labelled phosphatides present in the organs were 

 synthesised in situ. In the following, we will discuss how far this assump- 

 tion is justified. 



