Plasma Very Low Density Lipoprotein (VLDL) in Cholesterol-Fed Rabbits: Chylomicron Remnants or Liver Lipoproteins?

Abstract

When iodinated hypercholesterolemic plasma very low density lipoprotein (VLDL), chylomicrons or chylomicron remnants were injected intravenously, the apoB of chylomicrons and chylomicron remnants was removed more rapidly than apoB of hypercholesterolemic VLDL. In perfused livers from normal or cholesterol-fed rabbits, chylomicron remnants were removed 69% and 125% more rapidly, respectively, than hypercholesterolemic VLDL. Chylomicron remnants were removed equally well by perfused livers from normal and cholesterol-fed rabbits, but hypercho-lesterolemic plasma VLDL was removed more slowly by perfused livers of cholesterol-fed than by those of normal rabbits. Chylomicron remnant removal by livers from normal and cholesterol-fed rabbits was inhibited by high levels of hypercholesterolemic plasma VLDL in the perfusate. Twenty-four hours after a single dose of retinyl ester was fed to cholesterol-fed rabbits, less than 1% of the absorbed retinol remained in the plasma as retinyl ester. Thus, increases in plasma VLDL cholesterol levels in cholesterol-fed rabbits cannot be accounted for by the accumulation of chylomicron remnants. Apparently, a cholesterol-rich VLDL, probably of hepatic origin, accumulates in the postabsorptive plasma of the cholesterol-fed rabbit.