Intestinal absorption and lipoprotein transport of (omega-3) eicosapentaenoic acid

Adult male rats were surgically provided with a drainage catheter in the left thoracic lymphatic channel and an indwelling gastric catheter for constant infusion of saline-glucose. After an overnight fast, animals were given a single gastric dose of an aqueous emulsion containing one of the following 1-14C-labeled fatty acids: oleic, arachidonic or eicosapentaenoic acid, and [1,2-3H]cholesterol. Absorption was estimated by the appearance of radioactivity in lymph over a 24-h collection period, and the lymph lipoprotein distributions and lipoprotein lipid distribution were determined in the 24-h samples. Although there were apparent differences in the rates of eicosapentaenoic and arachidonic acid absorption, the overall appearance (after 24 h) of these acids in lymph was quantitatively equivalent to that of oleate. Furthermore, cholesterol absorption from each fatty acid medium was quantitatively similar. The distributions of each fatty acid among major lymph lipoproteins were similar with 93-95% recovered in chylomicrons and very low density lipoprotein (VLDL) fractions. Furthermore in these lipoproteins, 85-91% of each of the three fatty acids was recovered as triglycerides. With both polyunsaturated fatty acids, there was greater incorporation into phospholipids and their precursor partial glycerides than with oleate. These studies suggest that unesterified eicosapentaenoic acid is absorbed efficiently into the lymphatic system, and has lymph lipoprotein and lipid distribution comparable to those of the more typical mono- and polyunsaturated fatty acids.