THE COMPOSITION OF THE LIPOPROTEINS IN THE PLASMA OF RABBITS WITH HYPERCHOLESTEROLÆMIA OR TRITON WR-1339-INDUCED HYPERLIPÆMIA

¹ Department of Experimental Pathology, John Curtin School of Medical Research, Australian National University, Canberra

The lipoproteins in the plasma of rabbits with cholesterol-fed hypercholesterolæmia and with Triton-induced hyperlipæmia were separated in an ultracentrifuge into fractions at densities of 1·019, 1·063 and 1·200, and the protein, free cholesterol, cholesterol ester, triglyceride and phospholipid, of each fraction determined.

In the group with hypercholesterolæmia, as the total cholesterol in the plasma rose, the cholesterol in the high density lipoprotein fraction remained constant, that in the fraction of density 1·019—1·063 increased at first and then remained constant, while that in the fraction of density < 1·019 accounted for most of the increase. In Triton-induced hyperlipæmia, all the increased lipoprotein was in the fraction of density < 1·019. In composition the complexes of the fractions of density 1·063—1·200 and 1·019—1·063 remained fairly constant, whereas that of density < 1·019 varied with increasing total plasma lipid, indicating the presence of several lipoproteins with a fairly wide range of S_f values. Figures for the mean composition of each of the fractions show that in hypercholesterolæmic, the main increase in plasma lipid was cholesterol and cholesterol ester and it was distributed in the two fractions of density 1·019—1·063 and < 1·109, whereas in Triton-induced hyperlipæmia the increased lipid was mainly triglyceride and it was present in the fraction of density < 1·019.

The plasma from human patients with primary hypercholesterolæmia and hyperlipæmia and with similar disorders secondary to nephrosis and hypothyroidism was shown to fall into two groups approximately similar in composition to the experimental groups of rabbits.