Characterization of low density lipoprotein-like particle in the human aorta from grossly normal and atherosclerotic regions

Physical and chemical criteria of lipoproteins containing apolipoprotein B, extracted from human aortic intima, were compared with those of plasma low density lipoproteins (LDL). Homogenates of grossly normal intima and advanced atherosclerotic lesions were subjected to differential ultracentrifugation to isolate a d = 1.006-1.063 g/ml density fraction which was extensively characterized. By electroimmunoassay, over 90% of the recovered apolipoprotein B immunological reactivity was found in isolates from both plaques and normal intima. In isolates of plaque and normal intima, particles of the same size as LDL were found, although a small population of very large structures was also present in plaque fractions. Apolipoprotein composition was similar to that of plasma LDL except for the presence of human serum albumin in aortic isolates. Fractions from aorta demonstrated greater electrophoretic mobilities than LDL. The lipid composition of isolates from normal intima was similar to that of LDL. The lipid composition of plaque fractions showed a significant decrease in the cholesteryl ester to free cholesterol ratio and in the triglyceride content in comparison to LDL and to fractions from normal intima. The fatty acid pattern of the cholesteryl ester fraction from isolates of both normal and plaque aortic homogenates demonstrated a significant decrease in the linoleate to oleate ratio as compared to LDL. Our initial studies suggest that although aortic fractions are similar to LDL by certain criteria, some differences observed are more pronounced in fractions from lesions than from normal intima.