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 tissue, and brain but in only trace amounts in the liver. Indirect immunofluorescence localization studies were performed in murine and bovine tissues using a rabbit polyclonal anti-human VLDLR antibody. Immunoreactive VLDLR protein was detected in the endothelium of capillaries and small arterioles but not in veins or venules of bovine skeletal muscle, 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 detect any signal from nonendothelial cells in the liver or peripheral organs. The VLDLR was also expressed at high levels on the endothelial surface of bovine coronary arteries; in contrast, little or no staining was seen in aortic endothelium. Antibody staining of cultured bovine coronary artery endothelial cells demonstrated punctate cell-surface staining, as well as staining of large and small cytoplasmic vesicles. This tissue and cell pattern of expression suggests that the VLDLR plays a role in the transport of VLDL or another plasma constituent from the vascular compartment to adjacent tissues.