Effect of concentration of perfusing free fatty acid on arterial lipid synthesis in perfused normal and atherosclerotic rabbit aortas.

Normal and atherosclerotic rabbit aortas were perfused at physiological pressure for 1 hour with media containing various concentrations of [3H]oleic acid, between 0.5 and 2.0 mmoles/l, complexed to a fixed concentration 40 g/l of bovine serum albumin (BSA). The mass of free fatty acid (FFA), which entered the arterial wall and was subsequently utilised for lipid synthesis, was calculated from the measured specific activities of FFA in the perfusates. In normal tissue, at all concentrations of FFA in the perfusate, the highest rates of utilisation of perfusate FFA for arterial lipid synthesis were for phospholipids (PL) and triglycerides (TG), with only about 2% in cholesteryl esters (CE). In atherosclerotic tissue, at both low and high concentrations of perfusate FFA, about 25% of fatty acid entering arterial lipids was in CE. When the concentration of FFA in the perfusion medium was raised, the mass of FFA from the medium that was incorporated in the total arterial lipids, increased in both normal and atherosclerotic tissue. The increase was due in normal tissue, to significant increases in incorporation into FFA, lecithin (PC), phosphatidyl inositol (PI), phosphatidyl ethanolamine (PE), TG and CE, whilst in atherosclerotic tissue it was due to increased incorporation into PC, PI, TG and CE. The results suggest that raised concentrations of FFA in blood may increase the rate of synthesis of lipids in normal and atherosclerotic tissue and thus exacerbate the accumulation of certain lipids such as cholesteryl esters, in fatty streak lesions of atherosclerosis.