Determination of Serum Apolipoprotein A-IV Concentration by Quantitative Immunoelectrophoresis

Abstract

We purified human apolipoprotein (apo) A-IV from pooled serum of healthy subjects. The amino acid analysis and the pl of this apo A-IV agreed closely with other published data. In addition, we prepared specific antisera to apo A-IV and used them for immunophoretic quantitation of apo A-IV levels in serum. Serum samples were diluted two times with saline containing 1% Triton X-100. Within-and between-assay CVs, studied with five serum samples, were both not greater than 6%. There was no influence of freezing and thawing of serum on the measured values for apo A-IV. The mean value of serum apo A-IV in fasting healthy subjects was 10.9±2.5 mg/dl. In the study of apo A-IV distribution in serum by this study, apo A-IV was found only in the ultracentrifugal bottom fraction of serum from normolipidemic individuals, whereas a small amount of apo A-IV was also detected in the chylomicron fraction from hyperlipidemic ones. The apo A-IV concentrations could not be detectable in the other lipoprotein fractions by this assay technique.