TURNOVER OF PHOSPHATIDES 



35" 



for the 90-day-okl rat, we arrive at a lower limit of percentage turnover 

 of 3 per hour by making use of the data given in Table 5. This is a rough 

 estimate which indicates that the turnover rat(> is about 1/3 of that found 

 for the liver phosphatides. 



Table 5 contains data of the relative specific activities of the spleen 

 total P and phosphatide P and the plasma inorganic P, 1he spleen 

 inorganic P value being taken to be = 100. 



T.'VBLK 5. — Specific Activity of Spleen Phosphatidks 

 Experiment Taking 2 Hours 



The percentage ratio of the specific activities of the phosphatide P 

 and spleen inorganic P measured at the end of the experiment decreases 

 with the age of the rat, the decrease being more pronounced if we con- 

 sider the ratio of the percentage activities of the phosphatide P and 

 plasma inorganic P, as seen in Table 5. This decrease indicated a decreas- 

 ing permeability with age of the spleen cells to inorganic P, a fact 

 previously observed by Ahlstrom et al. (1944) and by Andre asen 

 and Ottesen (1945). 



