The Quantitative Significance of the Lymphatic Pathway in Transport of Absorbed Fatty Acids

The claim that the major portion of absorbed fat passes into the lymph stream is based on the classical experiment of Munk and Rosenstein carried out more than 50 years ago on a patient suffering from elephantiasis, in whom a lymphatic fistula developed in the left leg (1). From such a fistula, these workers were able to recover as much as 60 per cent of the fat of an ingested meal. Such a high recovery was not observed by later investigators in animal experiments. Eckstein, working with dogs fed emulsified olive oil, reported recoveries in thoracic duct lymph as high as 21 per cent in 12 hours, and 17 per cent in 6 hours (2). When he fed the dogs oleic and pahnitic acids, the recoveries were much lower. Since the dogs were anesthetized throughout the entire period of lymph collection, Eckstein was careful to point out that he did not expect fat absorption to be as good as it would have been under more normal conditions. Such low recoveries of absorbed fat in thoracic duct lymph of the dog were also observed by Little and Robinson (3). The availability of C14-labeled fatty acids, together with the development by Bolhnan et al. (4) of a method for collecting lymph from the ununesthetized rat, made possible a reinvestigation of this problem.