TURN'OVER OF LBCITHI.V, CEPHALIX AXD SPHINGOMYELIN 



321 



Table 4. — Specific Activity of the Cellilar Inorganic P .\nd Phosphatide 



P Extracted fro.m the Organ.s 



Rabbit III. — Weight: 2.3 kgm. 

 Iixtraveiious injection (luring 234 miii 



(») 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 witli 

 incorporation of extracellular inorganic P. 



Table 5. — Specific Activity of the Cellltlar Inorganic P and Phosphatidh 



P Extracted from the Organs 



Rabbit IV. — Weight: 2.5 kgm. 

 Intravenous injection dviring 215 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 witli 

 incorporation of extracellular inorganic P. 



Liver phosphatides 



Let us first consider the liver phosphatides. Apart from the liver, 

 an intense turnover is going on in the intestinal mucosa, and the possibi- 

 lity must be envisaged that the labelled phosphatides were carried 

 into the liver from the intestine by the plasma. The plasma was founrl 

 to contain only small amounts of labelled phosphatides, the specific 

 activity of the plasma phosphatide P being, after the lapse of 4 hours, 

 only 1/7 of that of the liver phosphatide P. This fact excludes the possi- 

 bihty that a substantial part of the labelled liver phosphatides was led 

 from the intestine or any other organ into the liver. Large amounts 



21 Hevesv 



