Phosphatide molecules, origin

During the postabsorptive phase 5.2 to 8.0 mg. phosphatide phosphorus is turned over per hour in the plasma of dogs weighing 6-9 kg. In experiments with rabbits, after the lapse of 4 hours, 29-38% of the labeled phosphatide molecules originally present in the plasma were found in the liver (81). In the course of 17 minutes, 65% of labeled phosphatides originally present in the plasma of the chick left the circulation (81). 

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. 

The origin of phosphatides of goat milk (15,16) was investigated along similar lines to studies of the origin of yolk phosphatides. Phosphatides extracted from milk a few hours after subcutaneous injection of labeled phosphate were found to be much more active than those present in the plasma. Thus, phosphatide molecules of the milk cannot have originated in the plasma, but must have been built up mainly in the mammary gland. The specific activity of the phosphatide phosphorus extracted from the... 

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