INTERACTION OF I'LASMA PHOSPHATE WITH THE PHOSPHORUS COMPOUNDS 489 



was found to be only \ of that of the plasma phosphatide P. The greatest 

 part of the active phosphatide molecules present in the plasma of the 

 hen could therefore not originate from the intestinal mucosa but must 

 have been formed in the Uver and, possibly to minor extent, in other 

 organs. As the plasma of the hen contains only about 20 mgm % phos- 

 phatide P, thus only | of that incorporated in the yolks daily, over 

 j" of the plasma phosphatides of the blood is removed from the latter, 

 in the course of a day, and replaced by newly formed molecules. If the 

 plasma phosphatides originate from the liver, after the lapse of a day, 

 the specific activity of the plasma phosphatide P should no longer differ 

 materially from that of the liver phosphatide P. In an experiment, in 

 which the hen was killed 28 hours after injecting the labelled phosphate, 

 the plasma phosphatide P showed a specific activity amounting to 82% 

 of that of the liver phosphatide P. When interpreting the low figure 

 found for the phosphatide turnover in the intestinal wall of the hen 

 compared with that found in the liver we have, however, to bear in 

 mind that the labelled inorganic phosphate reaches the digestive traci 

 at a later and thus more "diluted" (with inactive phosphate) state than 

 the liver. The active phosphate injected will be promptly carried to the 

 liver while it enters the intestine only in the form of saliva, gastric juice, 

 bile and pancreatic juice and, possibly to some extent, through the 

 intestinal wall^^Mnthe digestive tract. Therefore, when comparing the 

 specific activities of the liver phosphatide P with that of the intestinal 

 mucosa phosphatide P after injection of active phosphate we are apt to 

 overestimate the phosphatide turnover of the liver while, when feeding 

 the active sodium phosphate, we must expect the opposite to be the 

 case. 



A comparison of the specific activity of the liver inorganic P with 

 that of the liver phosphatide P leads to the result that, after the lapse 

 of 28 hours, the former was about two times greater than the latter. 

 Thus only less than half of the phosphatide molecules present in th(> 

 hen's liver was newly formed within that time, the rate of regeneration 

 of the tissue phosphatides being thus a comparatively slow process. 

 In experiments we carried out on human subjects, in the course of a day 

 less than 30% of the plasma phosphatides was renewed and a rough 

 estimate, taking into account the change of the spec, activity of the 

 phosphate with time, indicates that after the lapse of a week this frac- 

 tion is still less than one-half (comp. Table 8). 



We have already mentioned that in vitro experiments have shown 

 that in the blood only a minimal new formation of phosphatide 

 molecules takes place; the phosphatides present in the corpuscles must 

 therefore have been incorporated in the latter rluring their formation. 



WG. F. YorNGYUBG, Proc. Exp. Physiol. Med. 36, 230 (1932). 



