Influence of chain length and degree of unsaturation on plasma free fatty acid uptake by the perfused rat liver

Abstract

1. 1. The fractional uptake of free fatty acids by perfused liver is inversely related to the chain length and directly related to the number of double bonds in the molecule. 2. 2. The affinity of the liver for long chain free fatty acids is myristic > palmitoleic > linoleic > oleic ≅ palmitic > stearic. Partial in vitro extraction by charcoal of fatty acids bound to albumin shows similar behaviour supporting the view that the first step in the uptake of fatty acids by the cell is a non-selective, physical adsorption. Therefore, it is suggested that the rate of fractional uptake of the individual free fatty acids depends less on the selectivity of absorption to the cellular membrane than on the relative affinity of the individual fatty acids for the binding sites on the albumin molecule. 3. 3. The uptake of the total exchangeable pool of plasma free fatty acids by the liver can be measured rather accurately by using oleic or palmitic acid as tracer. 4. 4. The difference in the uptake of individual fatty acids could explain the finding that the proportion of stearic acid in the plasma is greater than in adipose tissue. At the same time, it can explain the relative variations (increase of stearic acid and decrease of oleic acid) observed when there is a fall in the plasma free fatty acids concentration.