A simple, sensitive technique for classification of apolipoprotein(a) isoforms by sodium dodecyl...

Lipoprotein(a) (Lp(a)) is a lipoprotein containing a unique glycoprotein, apolipoprotein(a) (apo(a)), which shows considerable heterogeneity of apparent molecular mass on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). A unifying classification of isoform has been lacking. A simple sensitive procedure for classifying apo(a) isoforms was developed in which the relative mobility of apo(a) on SDS-PAGE was related to that of apolipoprotein (apo) B-100 (Rf vs B). After Western blotting apo(a) bands were visualised by a sensitive double antibody technique employing commercial polyclonal antibodies (sheep antihuman Lp(a) antibody, alkaline phosphatase-linked donkey antisheep antibody). The technique was sensitive (lower limit of detection 0.02 micrograms apo(a)) and had good reproducibility (coefficient of variation 0.9-6.4%). Ten isoform mobilities are described (less than 0.35, 0.40, 0.50, 0.60, 0.70, 0.80, 1.0, 1.10, greater than 1.15). Individuals may have single or double band phenotypes. This classification is compatible with those previously described and the method is suitable for many laboratories, as it employs standard equipment and commercially available materials.