Flow cytofluorometric study of lipoprotein interactions with cultured endothelial cells

Accumulation of rhodamine B isothyocyanate-conjugated low density lipoproteins (R-LDL) in cultured endothelial cells from human umbilical cord was studied with a fluorescence activated cell sorter. R-LDL uptake was blocked at 0 degrees C, inhibited by addition of excess of nonlabeled low density lipoprotein, high density lipoprotein-2 or high density lipoprotein-3. High density lipoprotein-2 was about twice as effective in inhibition of R-LDL uptake as high density lipoprotein-3. Endothelial cells that formed a contact-inhibited monolayer lost the ability to incorporate R-LDL via a receptor-mediated pathway. Using R-LDL, it was possible to distinguish cells with different levels of R-LDL incorporation.