Analysis of the intestinal absorption of essential fatty acids in vivo in the rat

The absorption and competition kinetics of the essential fatty acids (EFAs) , linoleic acid (LA), alpha-linolenic acid (alpha LnA) and arachidonic acid (AA) in vivo were studied in the perfused rat jejunum. Uptake of each EFA on its own followed saturable kinetics at low luminal concentrations, sugge sting a facilitative transport process, the affinity of which increased wit h chain length and degree of unsaturation. Absorption of one EFA was enhanc ed by low, whilst competitively inhibited by high, concentrations of a seco nd EFA. Whereas LA and aLnA each interfered with the absorption of one anot her, both had little effect on AA. There was a strong inverse correlation b etween the relative unsaturation of an EFA and the change in Km of its abso rption observed upon inhibition with another EFA. Overall, the results indi cated a specific absorptive mechanism, probably involving a transport prote in, the affinity of which increased with the degree of unsaturation of the EFA. (C) 2000 Harcourt Publishers Ltd.