Canine Lipoproteins and Atherosclerosis: I. Isolation and Characterization of Plasma Lipoproteins from Control Dogs

Canine plasma lipoproteins were fractionated into four distinct classes by ultracentrifugation combined with Geon-Pevikon block electrophoresis and characterized with respect to physical and chemical properties. The distribution of plasma lipids and lipoproteins was quite unlike that in man, the dog having approximately five to six times as much high density as lower density lipoproteins. Despite the marked difference in distribution, human lipoprotein equivalents were present. Very low density lipoproteins (VLDL) isolated at density less than 1.006 g/ml were triglyceride-rich particles ranging in size from 260 to 900 Å in diameter. The density range from 1.006 to 1.063 g/ml contained two classes of lipoproteins: one closely resembled aolow density lipoprotein (LDL) with β mobility and a particle size of approximately 200 Å and the other (called HDL1) was closely related to the high density lipoproteins with respect to immunochemical reactivity, electrophoretic mobility, and apoprotein content. The HDL1 particles ranged in size from 100 to 350 Å in diameter and appeared to be unlike any of the commonly described human lipoproteins. High density lipoproteins called HDL2 isolated in the density range from 1.087 to 1.21 g/ml were protein-rich particles ranging in size from 55 to 85 Å. The apolipoprotein patterns of VLDL, LDL, and HDL2 on polyacrylamide gel electrophoresis were similar to those of the corresponding lipoproteins of man.