Characterization and measurement of human apolipoprotein A-II by radioimmunoassay

R. B. Goldberg, J. B. Karlin, D. J. Juhn, A. M. Scanu, C. Edelstein, A. H. Rubenstein

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Abstract

The development of a radioimmunoassay for apolipoprotein A-II (apo A-II) is described. Initial studies revealed a lack of immunological identity between purified apo A-II used as the standard and serum or HDL. Extensive testing of different buffers, standards, antisera, tracers, utilization of a detergent, and heating of sera failed to resolve the problem. Gel filtration of iodinated and noniodinated apo A-II on Sephadex G-100 columns showed that apo A-II, in dilute solution, elutes in a higher molecular zone than expected with a broad, assymetrical profile. The use of a subfraction of the tracer in the assay resulted in parallelism in the serum and standard dilution curves. The apo A-II assay was sensitive, specific and reproducible. Apo A-II added to sera was fully recovered and delipidation did not affect the immunoreactivity of either serum or HDL. Apo A-II contributed approximately 20% to the protein mass of HDL. Comparison of these results with those obtained by radial immunodiffusion, and with previously reported data, indicates that the reactivity of apo A-II in its native and delipidated forms may be markedly influenced by different immunologic methodologies and their specific reagents. Caution should thus be shown at present in assigning absolute concentrations to apo A-II in serum or HDL.

Original languageEnglish (US)
Pages (from-to)902-912
Number of pages11
JournalJournal of Lipid Research
Volume21
Issue number7
StatePublished - Dec 1 1980
Externally publishedYes

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ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology
  • Cell Biology

Cite this

Goldberg, R. B., Karlin, J. B., Juhn, D. J., Scanu, A. M., Edelstein, C., & Rubenstein, A. H. (1980). Characterization and measurement of human apolipoprotein A-II by radioimmunoassay. Journal of Lipid Research, 21(7), 902-912.