Enzymatic Determination of Cholesterol in Serum Lipoproteins

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Abstract
A new method for the quantitative determination of the cholesterol content of serum lipoproteins is described. Electrophoresis of the serum lipoproteins on agarose gel is followed by the enzymatic determination of the lipoprotein cholesterol. The cholesterol is released from the agarose pieces containing the lipoproteins by dissolving the agarose with HCl. No influence of the HCl on cholesterol, and no influence of the agarose degradation products on the enzyme reactions was observed. The analytical procedure is simple and only 20 .mu.l serum are required. The average coefficient of variation for the determination of the .beta.-lipoprotein cholesterol is < 4%, and it is < 8% in the pre-.beta.-lipoproteins of Type IV hyperlipidemic patients. The cholesterol contents found in the other lipoprotein fractions have to be interpreted as an approximation. Semiautomation seems possible. In preliminary studies, the cholesterol concentrations of the serum lipoproteins were determined in some control subjects and in some hyperlipidemic patients. The results are in good agreement with data obtained by ultracentrifuge studies performed by other investigators. The advantages of this new procedure and aspects of application are discussed.