Abstract
An increased level of low density lipoproreins (LDL) in the blood and an accumulation of oxidized-LDL (ox-LDL) in the subendothelium are well known factors of atherosclerosis. Endothelin (ET), a potent vasoconstrictor isolated from endothelial cells, is mitogenic for smooth muscle cells and may participate in atherogenesis by this process. In the present paper we study the effects of native LDL and ox-LDL on ET secretion by adult bovine aortic endothelial cells (ABAE). Native LDL stimulate ET secretion in a dose dependent manner between 25 and 200 μg/ml, while the effects of ox-LDL are complex. A low concentration (50 μg/ml) of highly ox-LDL induces ET secretion while a high concentration (100 μg/ml) does not induce the secretion and is cytotoxic. 100 μ/ml of slightly ox-LDL stimulates the secretion. Our data indicated that the LDL(B/E) receptor pathway is not involved in n-LDL induced ET secretion and are not conclusive on the role of the scavenger receptor pathway in ox-LDL induced ET secretion. Lysolecithin, an important surface lipid of ox-LDL is not involved in the stimulation of the peptide secretion. Lecithin slightly stimulates the secretion. These results indicate that native LDL and ox-LDL may regulate ET secretion by endothelial cells but further studies are necessary to determine the mechanism of induction of ET secretion.