EXPRESSION OF THE VLDL RECEPTOR IN ENDOTHELIAL-CELLS

In this article we describe the cellular distribution of the very low density lipoprotein receptor (VLDLR), a transmembrane protein that is expressed at high concentrations in skeletal muscle, heart, adipose ti ssue, and brain but in only trace amounts in the liver. Indirect immun ofluorescence localization studies were performed in murine and bovine tissues using a rabbit polyclonal anti-human VLDLR antibody. Immunore active VLDLR protein was detected in the endothelium of capillaries an d small arterioles but not in veins or venules of bovine skeletal musc le, heart, ovary, and brain. In the liver, there was intense staining of the capillaries and arterioles that supply the capsule and hepatic vessels but no staining of the sinusoidal surfaces. We failed to detec t any signal from nonendothelial cells in the liver or peripheral orga ns. The VLDLR was also expressed at high levels on the endothelial sur face of bovine coronary arteries; in contrast, little or no staining w as seen in aortic endothelium. Antibody staining of cultured bovine co ronary artery endothelial cells demonstrated punctate cell-surface sta ining, as well as staining of large and small cytoplasmic vesicles. Th is tissue and cell pattern of expression suggests that the VLDLR plays a role in the transport of VLDL or another plasma constituent from th e vascular compartment to adjacent tissues.