Differential intestinal absorption of two fatty acid isomers: elaidic and oleic acids.

The absorption of 14C-labeled oleic acid and 14C-labeled elaidic acid was studied in bile- and pancreatic juice-diverted adult rats. In some cases these acids were compared with 14C-labeled palmitic acid absorption. Sodium taurocholate-emulsified test infusates containing an equimolar mixture of monopalmitin and two fatty acids (oleic and elaidic or palmitic), one of which was 14C labeled, were infused through a duodenal canula. The chyle was collected from the mesenteric lymphatic vessel by plastic tubing. Among the three fatty acids studied, oleic acid exhibited the highest lymphatic recovery rate (43-50%). Elaidic and palmitic acids appeared more slowly and in lesser amounts (10-17%). Simultaneously, the highest amount of chylomicrons was observed when the lipid emulsion contained oleic acid alone; the lowest was observed when elaidic acid was the only unsaturated fatty acid. Experimental data have also shown that compared with elaidic acid, oleic acid is preferentially incorporated into the lymph triglycerides. We can conclude from the data presented that the enterocytic enzymes involved in the absorption of lipids show a high degree of specificity related to the fatty acid isomery, since the absorption of elaidic acid differs markedly from its isomer oleic acid.