374 V. BLOOD LIPIDS 



In many respects, a-lipoprotein resembles the lipoprotein isolated by 

 Macheboeuf 5,144 from horse serum. Both are readily soluble in water in 

 the absence of salts; the lipoprotein from horse serum also possesses a high 

 electrophoretic mobility, 164 in line with a-lipoprotein. The lipoprotein 

 originally prepared from horse serum had a lipid content of 50%, as com- 

 pared with a value of 35% for the a-lipoprotein prepared from human 

 plasma. However, in the preparations of lipoprotein from horse serum 

 made since World War II, only about 20% of lipids were found. 



(c) Elinin. Dandliker et al. 165 separated a lipoprotein from human eryth- 

 rocytes which was called elinin. This lipoprotein was found to consist of 

 large asymmetric particles. Elinin is of especial importance because of its 

 relationship to the Rh factor and to the A and B substances. 



(d) Lipovitellin. In a comprehensive study of the nature of the lipo- 

 protein from egg yolk, lipovitellin, Hawke and Lea 166 noted that it con- 

 tains the phospholipids, phosphatidylcholine, phosphatidylethanolamine, 

 and unsaturated acids. The fatty acids are much more highly unsaturated 

 than are those of the egg-yolk glycerides. Lipovitellin contains much less 

 cholesterol than do the lipoproteins of human serum; it appears to be con- 

 siderably more stable. The presence of glucose, lactose, and sucrose during 

 freeze-drying of lipovitellin prevented loss of solubility and denaturation. 167 



b. The Nature of the Lipid-Protein Combinations in Lipoproteins. It 

 is generally assumed that the lipids are adsorbed on the serum proteins 

 and that only weak combinations exist between these two components. 

 The osmotic pressure of the lipoprotein solutions has been brought to bear 

 to explain such a combination. Thus, on the one hand, Popjak and Mc- 

 Carthy 168 reported that the extraction of lipids from normal plasma does 

 not alter the colloid osmotic properties of serum proteins. On the other 

 hand, Macheboeuf 69 reported that lipemic sera from patients suffering from 

 lipoid nephrosis exerted a higher osmotic pressure per g. of protein than did 

 normal sera. In addition, Rabinowitch 169 suggested that cholesterol in the 

 serum of diabetics exerts an osmotic pressure. In a later communication, 

 Popjak 170 reconciles these divergent opinions by demonstrating that the 

 lipids do not exert an osmotic pressure in lipemic sera, but rather increase 



184 M. A. Macheboeuf, J. L. Delsal, P. Lepine, and J. Giuntini, Ann. Inst. Pasteur, 

 69, 321-333 (1943). 



166 W. B. Dandliker, M. Moskowitz, B. H. Zimm, and M. Calvin, /. Am. Chem. Soc , 

 72, 5587-5592 (1950). 



166 J. C. Hawke and C. H. Lea, Biochem. J., 54, 479-483 (1953). 



167 J. C. Hawke and C. H. Lea, Biochem. J., 54, 475-479 (1953). 



168 G. Popjak and E. F. McCarthy, Biochem. J., 87, 702-705 (1943). 

 . 169 I. M. Rabinowitch, Arch. Internal Med., 46, 752-767 (1930), 



170 G. Popjak, Biochem. J., 40, 789-803 (1946). 



