ADMINISTRATION MODALITIES AND INTESTINAL LYMPH ABSORPTION OF ARACHIDONIC-ACID IN RATS

We investigated the effects of the proportion of arachidonic acid on lymph lipoprotein synthesis in rats, when infused in the presence of lipids with varying degrees of saturation. A single dose of 90-mu-mol of lipid was administered intraduodenally and intestinal lymph was collected. Emulsion lipid constituents were 90-mu-mol of [C-14]arachidonic acid alone, or either 30-mu-mol of [C-14]arachidonic acid or 5-mu-mol of [C-14]arachidonic acid and 25-mu-mol of linoleic acid, with 30-mu-mol of a free fatty acid and 30-mu-mol of a monoglyceride (the more saturated: oleic acid + monopalmitin; the more unsaturated: linoleic acid + monoolein). Radioactive lymph recovery of [C-14]arachidonic acid infused alone reached 32.6 +/- 1.3% of the radioactivity administered and the presence of another fatty acid and a monoglyceride increased it from 38.7 +/- 2.6 to 51.9 +/- 1.1%. For 30-mu-mol of arachidonic acid, integration into lymph phospholipids was higher when arachidonic acid was infused with oleic acid and monopalmitin than with linoleic acid and monoolein (7.3 +/- 2.7 and 2.8 +/- 0.2% at the absorption peaks, respectively), and it was 4.8 +/- 0.5% when arachidonic acid was infused alone. For 5-mu-mol of arachidonic acid, the degree of unsaturation of the added lipid did not modify phospholipid incorporation, which was maintained at 6.9 to 7.2%. The proportion and size of chylomicrons increased with the degree of lipid emulsion unsaturation. Percentages of [C-14]phospholipids and of chylomicrons were highly correlated. The proportion of arachidonic acid and degree of lipid emulsion unsaturation affected lymphatic arachidonic acid absorption modalities.