260 



ADVENTURES IN RADIOISOTOPE RESEARCH 



however, in the experiments in vitro no definite difference was found 

 in the formation of phosphatides in normal and lipaemic bloods, in the 

 perfusion experiment about three times as many newly formed phospha- 

 tide molecules were found to be present in the lipaemic blood as in the 

 normal. This result is supported by figures obtained when investigating 

 the labelled phosphatides extracted from the livers used in the perfusion 

 experiments. Here also (see Table 2) a greater part of the phosphatide 

 present became labelled when lipaemic blood was used. 



Tablk 2 



The livers used were taken from fasting cats, except in Exp. 3. In 

 Exp. 6 the specific activities of the ester P of the liver and the protein 

 P (remaining P after extraction with ether-alcohol and trichloroacetic 

 acid) were determined as well. The relative figures ol)tained were; speci- 

 fic activity of the inorganic P, 1; of the ester P, 0.218; of the protein 

 P, 0.068. The radioactive P atoms can only enter into the phosphatide 

 molecules by a synthetic process. If the radioactivity of 1 mgm organic 

 P of the liver were equal to that of 1 mgm inorganic P, all organic P atoms 

 would have been replaced. If the organic P were not radioactive at all, 

 none of the organic molecules could be newly formed. If all the phospha- 

 tide molecules present in the liver after the perfusion experiment had 

 been newly formed the value of the ratio in the last column would be 1. 

 From the figures it follows that 1.5% of all phosphatide molecules pre- 

 sent in the experiment with normal blood and 2.7% in that with lipaemic 

 })lood are formed in the course of the experiment. 



During the perfusion experiment some molecules may have decom- 

 posed thus introducing an uncertainty into all conclusions based on the 

 determination of the amount of phosphatides present. Our conclusions 



