Modulation of membrane composition of swine vascular smooth muscle cells by homologous lipoproteins in culture.
Swine vascular smooth muscle cells were exposed to homologous low-density or high-density lipoprotein fractions for 24 h. Total cell membranes were isolated from the post-nuclear supernatant of the cell homogenates, fractionated by sucrose denisty gradient centrifugation and characterized by enzyme assays. The membrane fraction with the lowest density was enriched in plasma membrane marker enzymes. Cholesterol analysis showed that cells exposed to low-density lipoprotein had higher cholesterol-to-protein ratios in total cells, total cell membranes and individual membrane fractions than had the cells exposed to high-density lipoproteins. Cholesterol-to-phospholipid ratios of the plasma membrane-enriched fraction from cells exposed to low-density lipoprotein were higher than the same membrane fraction of cells exposed to high-density lipoprotein. Studies with iodinated lipoproteins showed that these compositional changes could not be due to lipoprotein contamination. Membrane microviscosity was determined by fluorescence depolarization with diphenylhextriene and the microviscosity of the plasma membrane-enriched fraction was different in the cells exposed to the two different lipoprotein fractions. This difference in membrane microviscosity was significant only when the medium cholesterol content was 40 micrograms per ml or greater; cells exposed to low-density lipoprotein gave membranes with higher microviscosity. These results demonstrate that the properties of vascular smooth muscle cell membranes are influcenced by exposure of the cells to homologous lipoprotein fractions.
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D008074:Lipoproteins / Q000097:blood / Q000494:pharmacology*; D008075:Lipoproteins, HDL / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000494:pharmacology; D008560:Membrane Fluidity / Q000187:drug effects*; D008563:Membrane Lipids / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D013552:Swine
D008074:Lipoproteins; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D008563:Membrane Lipids; D002784:Cholesterol