Analysis of Lipoprotein a

Observations in different types of primary hyperlipidemia revealed in general an inverse correlation between Lp(a) concentrations and plasma triglyceride and triglyceride-rich lipoprotein concentrations in hypertriglyceridemic subjects (A 10, B22, H30, W11). As far as this observation is not troubled by technical problems in the analysis (E8), the possibility exists that Lp(a) catabolism is partly related to the catabolism of triglyceride-rich and/or cholesterol-rich particles (P10, R16). 

Lp(a) measurements have found a wide range of applications since most of the structure, physiology, and genetics of this unusual lipoprotein class were unraveled (S14). 

The discovery of Lp(a) by Berg in 1962 (B6) relied on the production of rabbit antisera against beta-lipoprotein and on the selective absorption of these antisera with individual human sera. When certain human sera were used for absorption, the antisera retained precipitation capacity in radial immunodiffusion with 30-35% of individual human sera, which obviously contained a previous unknown antigen. The particle carrying the new antigen shared antigenic properties with beta-lipoprotein, but had an additional antigenic structure. This was evidenced from the only partial fusion of the precipitin bands formed between a positive human serum, the antibeta lipoprotein antiserum and the new absorbed antiserum. 

After the first distinction, made by Berg (B6), between Lp(a) positive and Lp(a) negative sera, Harvie et al. (H18), using isopycnic ultracentrifugation, demonstrated that after concentration, a significant amount of Lp(a) could be detected in Lp(a)-negative sera. 

In plasma, Lp(a) moves with a pre-beta-1 mobility (B8, B9) and has been referred to as the sinking pre-beta fraction, as it shares the mobility of VLDL yet does not float at the same density in the ultracentrifuge. Serum electrophoresis followed by a lipid staining with Oil Red O or Fat Red should be a convenient method for detection of elevated Lp(a) levels. Sample collection and preservation are, however, critical parameters in this assay (B26, K9). 

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