Absorption of Oleic and Palmitic Acids from Emulsions and Micellar Solutions

acid-1-14C, and palmitic acid-9,10-3H) was infused intraduodenally at a steady rate for 8 hr in fasted, unanesthetized rats. The same dose of lipid was given together with pure conjugated bile salts either as an emulsion, 2.5 mm bile salts, or as a micellar solution, 10 mm bile salts. The emulsion contained very little or no micellar lipid. Thoracic duct lymph was collected and in some experiments bile and pancreatic juice were drained to the ex-terior. After 4-5 hr infusion the same steady lymphatic output of radioactive fatty acids was obtained with emulsion as with micellar solution. It was concluded that absorption of fatty acid could proceed efficiently in the virtual absence of micellar solubilization. In rats with biliary plus pancreatic fistulae, labeled triglyceride was ab-sorbed poorly relative to free fatty acids in the same emulsified particles. This suggested that fatty acids were transferred to the absorptive cells in monomolecular solution and not as emulsion particles. Substitution of a synthetic nonionic detergent for bile salts in lipid mixtures given to rats with biliary and pancreatic fistulae did not affect the lymphatic output of radioactive fatty acids. This indicated that mucosal esterification of labeled free fatty acids was normal in the absence of bile salts. The physical state of the lipid did not affect the pathway of absorption. Finally, comparison of the increased output of esterified fat in the lymph with Address requests for reprints to Dr. W. J. Simmonds