Radioimmunoassay of rat apolipoprotein B peptides in lipoproteins and tissues

✍ Scribed by Nancy L. Young; Philip W. Harvey; John Elovson

• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 601 KB
• Volume: 162
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(87)90397-6

✦ Synopsis

Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE) separates rat apoliprotein B (apoB) into one lower and two higher molecular weight components. Of the latter, peptide I (PI) corresponds to human B-100, while the slightly faster-migrating peptide II (PII) lacks a human counterpart; the smaller species peptide III (PIII) corresponds to human B-48. We describe here a competitive radioimmunoassay which separately measures the amounts of total (i.e., PI + PI1 + PIII) and larger (i.e., PI + PII) rat apoB peptides, with the amounts of PI11 obtained by difference. Standard rat PI11 and combined PI + PI1 (PI,II) were isolated by high-pressure gel filtration liquid chromatography in the presence of SDS, and the PI,11 was used as an immunogen to raise rabbit antisera which were capable of binding all three forms of rat apoB. However, Scatchard analysis showed this binding to represent two distinct types of antibodies: one high-affinity class which bound only PI,11 and a second class which bound all apoB peptides with equal but lower affinity. Thus, since '2sI-labeled PI11 was displaced equally effectively by PI,11 and PIII, but '2SI-labeled PI,11 was displaced only by PI,II, the unabsorbed antiserum could be used to measure either total apoB or PI,11 alone, depending on the choice of labeled ligand. The validity of the assay for apoB peptides in very-low-density and low-density lipoproteins and in liver microsomes was verified by comparison with peptide determinations by SDS-PAGE. o 1987 Academic RW, IK.