Effect of high density lipoproteins on permeability of rabbit aorta to low density lipoproteins

A study was made on the effect of high density lipoproteins (HDL) on the permeability of rabbit aorta to low density lipoproteins (LDL) after intravenous administration of human HDL and human [125I]LDL to normal and hypercholesterolemic rabbits. Evaluation of radioactivity in plasma and aorta has shown that the administration of a large dose of HDL decreased the aorta permeability rate for [125I]LDL on an average by 19% in normal rabbits, and by 45% in rabbits with moderate hypercholesterolemia. A historadiographic study showed that HDL also decreased the vessel wall permeability to [125I]LDL in normal and particularly in hypercholesterolemic animals. The suggestion was made that HDL at very high molar concentration can hamper LDL transportation through the intact endothelial layer into the intima due to the ability of HDL to compete with LDL in sites of low affinity on the surface of endothelial cells.