Isolation and characterization of the major lipoprotein density classes of normal and diabetic baboon (Papio anubis) plasma

Lipoproteins from the plasma of normal and diabetic baboons (Papio anubis) were separated into very low density lipoproteins (VLDL, d 1.006 g/ml), low density lipoproteins (LDL, d 1.006-1.063 g/ml) and high density lipoproteins (HDL, d 1.063-1.21 g/ml) and the density classes were characterized by immunologic methods and by quantitative determination of protein and lipid. Diabetes was induced by surgical removal of the pancreas and the hyperglycemia was controlled by daily insulin injection. HDL were the major density class of normal baboon plasma representing 66% of the total lipoprotein content. LDL accounted for 31% and the VLDL for only 3%. Diabetes had a profound effect on the distribution of baboon lipoproteins. VLDL accounted for 37%, LDL for 35% and HDL for only 28% of the total lipoprotein content. In normal baboons, HDL was the main vehicle for the transport of phospholipids and glycerides with cholesterol almost equally distributed between HDL and LDL. In diabetic animals, free and esterified cholesterol were transported mainly by LDL and the glycerides by VLDL. Cholesterol esters accounted for approximately 75% of the total cholesterol in both the normal and diabetic baboons. Studies on the immunologic properties of baboon lipoproteins showed a marked heterogeneity of all 3 major density classes with respect to antigenic composition. Antisera to human apolipoproteins A (A-I and A-II), B, C (C-I, C-II and C-III), D and E cross-reacted with baboon lipoproteins suggesting a close analogy between apolipoproteins of these two species.