Lipoproteins in human atherosclerotic vessels. I. Biochemical properties of arterial low density lipoproteins, very low density lipoproteins, and high density lipoproteins
Hollander, W.; Paddock, J.; Colombo, M.
Experimental and Molecular Pathology 30(2): 144-171
ISSN/ISBN: 0014-4800 PMID: 217725 DOI: 10.1016/0014-4800(79)90051-0
Lipoproteins extracted from the human aortic intima into 1.65 M NaCl were quantitated and characterized biochemically and by EM following separation in the preparative ultracentrifuge. The arterial lipoproteins, although separated and designated according to the density classes used for the serum lipoproteins, were distinctly different from serum lipoprotein. The amount of lipoproteins in the low density range of d (density) 1.063-1.006 (arterial LDL) and in the very low density range of d < 1.006 (arterial VLDL) extracted from arterial intima increased with increasing intimal lipid content. The concentration of lipoproteins in the high density range of d 1.210-1.063 (arterial HDL) was small and did not change with the severity of atherosclerosis. Arterial VLDL, LDL and its subfractions, LDL1 (d 1.006-1.019) and LDL2 (d 1.019-1.063), were markedly heterogenous and contained unusually large particles, which were isolated by Bio-Gel A-150. The particles showed a pitted and cratered appearance by scanning electron microscopy and were immunochemically unrective and had no electrophoretic mobility. The lipid and amino acid composition of the arterial VLDL and LDL fractions and their electrophoretic, chromatographic and analytical flotation behavior was distinctly different from that of their serum lipoprotein counterparts. Arterial VLDL, in sharp contrast to serum VLDL, was rich in cholesteryl ester and poor in triglycerides. Arterial VLDL also showed no electrophoretic mobility and only 1/2 of the preparations reacted to LDL antisera. Acid mucopolysaccharides were detected in the arterial VLDL and LDL fractions in association with the large size particles which lacked electrophoretic mobility and immunochemical reactivity and showed a saw tooth pattern in the analytical ultracentrifuge. Arterial LDL and LDL2 contained a smaller sized population of particles as separated by Bio-Gel A-150, the particles showed a reaction of complete identity with serum LDL when reacted against LDL antiserum but had a greater electrophoretic mobility and different amino acid composition than did serum LDL and LDL2. An asymmetrical peak with a mean sedimentation coefficient (SF) of 7.3 was shown by these particles in the analytical ultracentrifuge. Lipid deposition in atherosclerotic plaques is apparently associated with the accumulation of lipoproteins with biochemical and ultrastructural properties unlike those of serum lipoproteins. The presence of these lipoproteins in the arteries may be a result of the interaction of serum and arterial lipoproteins with acid mucopolysaccharides and of lipoprotein synthesis and degradation in the arteries.