Linoleic acid chyloportal partition and metabolism during its intestinal absorption

1-14C linoleic acid intestinal absorption and simultaneous biochemical events were followed up on rats under vascular perfusion and on main mesenteric lymphatic duct fistulated rats. 1-14C linoleic acid was introduced in the duodenum alone in doses from 1.2 to 90 mumol or in the presence of oleic acid and monopalmitin (30/30/30 mumol/mumol/mumol). Mesenteric portal venous blood and chyle, respectively, were collected continuously for 1 and 6 h after the infusions. Blood-labeled lipid recovery varied from 4.7 to 2.2% of the 14C linoleic acid infused as the 14C linoleic acid dose infused increased, and dropped to 1.8% with the mixed lipid infusate. Lymph-labeled lipid recovery increased from 25.7 to 31.8% of the 14C linoleic acid infused as the dose infused increased, and rose to 48.1% with the mixed lipid infusate. The oxidation of 1-14C linoleic acid remained low: 0.8-3% of the infused radioactivity. A desaturation and elongation of 14C linoleic acid into 14C arachidonic acid was detected and discussed. We can conclude that the linoleic lymph absorption pathway remained preferential in our experimental conditions, simultaneous to a low rate of oxidation and an eventual ability for the enterocyte to convert this essential fatty acid arachidonic acid.