Key Points
- To develop and validate a double antibody radioimmunoassay for quantifying total plasma apolipoprotein B (ApoB) across various lipoprotein classes in healthy and hyperlipoproteinemic human subjects.
- Developed a double antibody radioimmunoassay (RIA) targeting human ApoB across low-density lipoproteins (LDL), very-low-density lipoproteins (VLDL), and chylomicrons.
- Assessed displacement curves of purified lipoproteins, animal sera, abetalipoproteinemic plasma, and human plasma samples from normal subjects and individuals with Type II, IV, and V hyperlipoproteinemia.
- Quantified ApoB distribution across density fractions (d > 1.006) and evaluated temporal stability in patients maintaining a constant diet and medication regimen.
- ApoB accounted for approximately 25% and 35% of total protein in chylomicrons and VLDL, respectively, displaying immunological identity across chylomicrons, VLDL, and LDL in both normal and hyperlipoproteinemic plasma.
- Fasting total plasma ApoB averaged 83 +/- 16 mg/dl in normal subjects, but was elevated in Type II (162 +/- 16 mg/dl), Type IV (112 +/- 24 mg/dl), and Type V (105 +/- 17 mg/dl) hyperlipoproteinemia.
- Greater than 90% of ApoB resided in the d > 1.006 plasma fraction in normal and Type II subjects, compared to only 50% to 80% in Types IV and V, demonstrating that hypertriglyceridemia mainly involves ApoB redistribution to lighter density fractions while hypercholesterolemia markedly increases absolute ApoB.
Structured PICO
PPopulationNormal subjects and subjects with hyperlipoproteinemia (Types II, IV, and V)
IInterventionDouble antibody radioimmunoassay (RIA) for human apolipoprotein B (ApoB)
OOutcomeTotal plasma ApoB concentrationsurrogate
The development of a radioimmunoassay for ApoB demonstrates that ApoB concentrations are significantly elevated in hypercholesterolemia and hypertriglyceridemia, with different distribution patterns among lipoprotein fractions.