LDL, scavenger, and beta-VLDL receptors on aortic endothelial cells

Abstract

Primary and first passage aortic endothelial cells were shown to possess a high affinity receptor for beta-migrating very low density lipoproteins (beta-VLDL) distinct from the low density lipoprotein (LDL) receptor and scavenger receptor on these cells. In bovine aortic endothelial cells, 125I-rabbit beta-VLDL was taken up and degraded by a high affinity process that was competed for by unlabeled rabbit beta-VLDL and unlabeled postprandial VLDL from a fat-fed normal subject. However, unlabeled human or rabbit LDL, human LDL modified by malondialdehyde (MDA-LDL), or VLDL from a fasted normal human or a rabbit were not effective competitors for the degradation of 125I-rabbit beta-VLDL. In contrast to the receptor-mediated degradation of 125I-human or rabbit LDL and 125I-human-MDA-LDL, cell density did not affect the receptor-mediated degradation of 125I-rabbit beta-VLDL. Endothelial cells from a Watanabe heritable hyperlipidemic (WHHL) rabbit virtually did not degrade rabbit LDL, but degraded rabbit beta-VLDL at a rate equal to that seen in normal rabbit endothelial cells. It was concluded that the beta-VLDL receptor on endothelial cells is genetically distinct from the LDL receptor. Incubation of cells for 3 days with 100 micrograms/ml protein of unlabeled beta-VLDL caused an 88% increase in cellular cholesterol content, even though the beta-VLDL receptor activity was down-regulated by 60%. Endothelial cells and monocyte-macrophages are thus far the only cells known to possess the LDL receptor, the scavenger receptor, and the beta-VLDL receptor.