Low density lipoprotein heterogeneity in the cebus monkey.

Abstract

In studies of cebus monkey plasma lipoproteins, we have used an ultracentrifugally generated density gradient to isolate two distinct species of low density lipoproteins (LDL). Compositional analyses revealed that each of the ultracentrifugally isolated fractions was enriched in cholesteryl esters and contained a single apolipoprotein which in terms of its mobility on SDS gels corresponded to apolipoprotein B-100, the major apolipoprotein of human LDL. Hydrodynamic measurements carried out in the analytical ultracentrifuge showed that F1.20 values were 30.0 for LDL1 and 23.5 for LDL2. In a solution of density 1.0069 g/ml, the sedimentation rates were 5.9 and 7.2 S for LDL1 and LDL2, respectively. In addition to sedimentation velocity data, we describe a new approach for using these same data to obtain calculated values for molecular weight. The hydrated densities calculated for the two fractions were 1.033 and 1.045 g/ml and calculated molecular weights were 3.08 million for LDL1 and 2.42 million for LDL2. Hydrated density values were in excellent agreement with those calculated from compositional data. Electron microscopy data showed that LDL1 had a larger mean diameter of 26.7 nm than LDL2 which had a diameter of 19.3 nm. Native gel electrophoretic analyses of the two LDL fractions in 3.5% acrylamide showed that, consistent with its size, LDL1 had slower mobility than LDL2.