Passage of Phosphatides into Lymphatic Channels

As mentioned above, in the course of few hours a very appreciable part of the phosphatide molecules originally present in the plasma are found to be replaced mainly by phosphatide molecules previously present in the liver. Reinhardt et al. (146) found that part of the labeled phosphatide molecules injected into plasma reached lymphatic channels and were recovered in the thoracic duct lymph. It is not established through which tissues phosphatides migrate, although liver presumably plays an important part in this process. Some figures for the recovery of injected labeled plasma phosphatides are seen in Table XXIV. 

Recovebv op Injected Plasma Radiophosphatidb in Thoracic Duct Lvmph 

Interval after injection of plasma, min. Total lymph collected, ml. Phosphatide expressed as radioactive counts/min. Phosphatide P ex-pressed as radioactive counts, min./m . 

The dog received intravenously 100 ml. of plasma containing a total of 759,200 counts per minute as phosphatide. The first sample of lymph was obtained during the first 36 minutes after the injection of radiophosphatide. This sample already contained over 2000 counts per minute. If we assume that plasma represents 5% of the body weight, the plasma still contained a total of 452,000 counts per minute at the end of this period of observation. Approximately 9% of the phosphatides that left the plasma was recovered from the lymph of the thoracic duct in the course of six hours and still higher figures (20%) were obtained in experiments with other dogs. Thus thoracic duct lymph serves as a medium for the return to the plasma of a significant fraction of the phosphatides lost from the plasma. 

About two hours after administration of a meal containing fat, the fat content and phosphatide content of the blood begins to rise. A maximum is reached after four hours (22). The increase in lecithin content of the plasma could be due to lecithin synthe.sized in the intestinal mucosa and absorbed into the blood or to mobilization of phosphatides synthesized in the liver or other organs. 

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