The contribution of serum phosphatidylcholine and lysophosphatidylcholine to lymph phosphatidylcholine

1. The contribution of serum phosphatidylcholine and 1-acyl lysophosphatidylcholine to chylomicron and mesenteric lymph lipoproteins of heavier buoyant density was studied in rats with catheters placed in the jugular vein, duodenum, common bile duct and mesenteric lymph duct. The effect of including 10 mM phosphatidylcholine in the triolein emulsion infused into the duodenum was also studied. 2. The intravenous infusion of phosphatidylcholine did not affect delivery of phosphatidylcholine into the lymph when phosphatidylcholine was included in the duodenal infusion. However, on intravenous lysophosphatidylcholine infusion, phosphatidylcholine transport into the lymph was increased both in chylomicrons and the other lipoproteins found in the lymph when phosphatidylcholine was included in the duodenal infusion. 3. The incorporation of serum phosphatidylcholine into chylomicron phosphatidylcholine was minimal and decreased further by intraduodenal phosphatidylcholine infusion. Incorporation into the heavier lymph lipoproteins was less than 20%. 4. The incorporation of serum lysophosphatidylcholine into chylomicrons was 17% at 4--6 h of infusion which was decreased by intraduodenal phosphatidylcholine as was the incorporation into the heavier lipoproteins of lymph. 5. It is concluded that serum phosphatidylcholine is a poor precursor of chylomicron phosphatidylcholine and that while lysophosphatidylcholine is a somewhat better precursor, its contribution to chylomicron phosphatidylcholine is limited by its serum concentration.