Quantitation of serum lipoproteins by electrophoresis on agarose gel: standardization in lipoprotein concentration units (mg/100 ml) by comparison with analytical ultracentrifugation

Abstract

Lipoprotein electrophoresis on agarose gel has been modified to allow estimation of the absolute quantity of each fraction. The reproducibility of the method is illustrated by 12 determinations in a single day on serum from one normal subject: mean total dye uptake was 302 ± (sd) “corrected dye units,” and the percentages of β-, pre-β, and α-lipoprotein were 56.1 ± 0.9, 29.1 ± 0.4, and 14.8 ± 0.7, respectively. Reproducibility over a period of 8 months was also demonstrated.Serum lipoproteins of five normal and 15 hyperlipidemic individuals determined by this technique were compared with values obtained by analytical ultracentrifugation. The correlation coefficients were: 0.993 for pre-²-LP vs. VLDL, 0.978 for ²-LP vs. LDL, and 0.867 for ±-LP vs. HDL. Lipoprotein values obtained by paper electrophoresis were also correlated with those of the analytical ultracentrifuge, but to a lesser degree (r = 0.956, 0.691, and 0.786, respectively). Values for LDL and VLDL which were measured by refractometry after preparative ultracentrifugation were very similar to those obtained from the analytical ultracentrifuge. Serum triglyceride concentration was highly correlated (r = 0.972) with the agarose values for pre-²-LP; serum cholesterol concentration was correlated (r = 0.673) with ²-LP. It is proposed that the standard curves of the comparisons with the analytical ultracentrifugal values be used to convert the corrected dye units of electrophoresis on agarose gel to mg/100 ml of specific lipoprotein.

Keywords

• cholesterol
• gravimetric total lipids
• paper electrophoresis
• refractometry
• triglyceride