Separation and Properties of Pig-Serum Lipoproteins

Pig serum contained three major classes of lipoproteins resembling the very low density (VLDL), low density (LDL), and high density lipoproteins (HDL) found in human serum but in smaller amounts. The LDL class had two clearly resolved components (LDL 1 and LDL 2 ) that were separated by differential centrifugation at solvent densities of 1.060 and 1.090. Heterogeneity in density was evident in all fractions, especially in those of highest lipid content. Average molecular weights and lipid contents of the isolated fractions were: VLDL, 17 × 10 6 and 90%; LDL 1 , 3 × 10 6 and 79%; LDL 2 , 2 × 10 6 and 72%; and HDL, 0.25 × 10 6 and 51%. Apart from small differences in proportion, the lipoproteins in the pooled samples collected over an 18-month period were quite similar although more extensive measurements may reveal differences. The presence of these distinct and separable lipoprotein fractions suggest structural differences worthy of further study.