ABSTRACT
The successful delivery of drugs to desired sites of action implies complex interactions and passage through cell barriers among which the vascular endothelium is of paramount importance. The use of lipoproteins (LPs) as natural carriers for delivery of lipophilic drugs raises several issues regarding the endothelial transport of LPs in different tissues and in various physiopathological conditions. Once secreted by the small intestine and the liver, LPs undergo rapid transformations in plasma either by physical transfer of lipid and apoprotein components or by enzymatic catalysis by lecithin-cholesterol acyltransfe-rase and lipoprotein lipase. Together with newly synthesized apolipoproteins A and B-48, they are assembled into large polymorphic particles, the nascent chylomicrons. In spontaneously hyperlipoproteinemic old Spraque-Dawley rats in which plasma native LPs were rendered visible by mordanting the tissue specimens with tannic acid. In normal conditions, transcytosis of macromolecules including LP largely prevails over endocytosis of the same molecular species.
