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ADVENTURES IN EADIOISOTOPE RESEARCH 



formation into a tissue containing labelled phosphatides. Some of the 

 labelled phosphatide molecules came into the corpuscles after they 

 reached the circulation. As seen in Table 12, in which the results of 

 some experiments in vitro are recorded, a part of the phosphatide 

 molecules of the corpuscles exchanges easily with those of the plasma. 

 Presumably those situated in the outermost layer of the stroma take 

 part in this exchange process. It is, however, rather difficult to interpret 

 the comparatively high specific activity of the phosphatide P extracted 

 from the corpuscles in experiments in vivo without assuming that 

 a phosphatide turnover takes place in the corpuscles, though the rate 

 of this turnover is small compared with that of most of the acid-soluble 

 P compounds present in the corpuscles (see Table 14). 



Table 13 — Extent of Partition of Labelled 

 Phosphatides, Originally Present in the Plasma, 



BETWEEN the PHOSPHATIDES OF THE CoRPTJSCLES 

 AND OF THE PlASMA IN EXPERIMENTS in vivO 



In experiments in vivo with rabbits (see Table 13), in the course of a 

 day, the activity of the corpuscle phosphatide P was found to be only 

 about 1/6 of that of the plasma phosphatide P. A still greater difference 

 was found when investigating chickens blood. 



Using elaidic acid as an indicator, Sinclair^i) found, 8 hours after 

 ingestion of the elaidic acid, 15 per cent of the fatty acids extracted 

 from the plasma phosphatides to be composed of this distinctive fatty 

 acid, while the corpuscles contained no more than traces of the indicator. 



When iodised fatty acid was used as an indicator, it was found^^) not 

 only in the phosphatides of the plasma but also in those of the cor- 

 puscles. In the latter, the concentration of iodised fat was even higher 

 (3.3 per cent of the 1otal fatty acids) than in the former (2.0 per cent). 

 The application of iodised fatty acids leads, thus, to a result which is in 



(i>R. G. Sinclair, J. Biol. Chem. 115, 211 (1930). 

 (2)C. Abtom, Arch. Int. Physiol. 36, 101 (1933). 



