CELLULAR TRANSPORT OF LONG CHAIN FATTY ACIDS

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Abstract
Cellular transport of long chain nonesterified fatty acids involves transfer of fatty acids between extracellular binding sites on albumin and tissue binding sites on cell membranes and organelles. Tissue phospholipids and lower glycerides do not serve as primary acceptors for fatty acid entering the cell. Evidence for an energy-dependent transport process is lacking; however, alterations in active cellular metabolism which influence utilization of fatty acids may indirectly affect transport by changing the rate of clearance of fatty acids from tissue binding sites. Release of nonesterified fatty acids from adipose tissue, and uptake by heart muscle and other tissues are influenced by fatty acid concentration and the molar ratio of fatty acid to albumin in extracellular fluid, and probably as well by the capacity and turnover rate of binding sites for fatty acid within the cells. The relationship between transport and molecular structure of fatty acids may be attributed to differences in solubility, protein binding, and rate of intracellular utilization of fatty acids of different chain length and degree of unsaturation. Removal of circulating triglyceride appears to be influenced by lipoprotein lipase activity of peripheral tissues but may be limited by the capacity of the tissue to accept the component fatty acids.