Determination of apolipoprotein B-48 in plasma by a competitive ELISA.

BACKGROUND Apolipoprotein B-48 (apoB-48) is produced by the small intestine, as part of chylomicrons, and appears to be a suitable marker for clinical studies of postprandial lipoproteins and related cardiovascular risk. Our aim was to develop, for routine analysis, an assay to quantify apoB-48 in plasma samples. METHODS A microtiter plate was coated with a C-terminal apoB-48-specific heptapeptide. Plasma samples were incubated with appropriate detergent to allow competition between immobilized antigen and plasma apoB-48. Appropriate calibration curves were obtained in the ELISA, using calibrated lymph and chylomicrons. RESULTS Treatment of plasma samples with the mild detergent Triton X-100 allowed an efficient competition between immobilized antigen and plasma apoB-48. No cross-reactivity was found with apoB-100, as checked by ELISA and Western blot analysis. Intra- and interassay CVs were 5.4% and 5. 5%, respectively. In healthy subjects, apoB-48 concentrations markedly increased in the postprandial state, in parallel with triglycerides. CONCLUSIONS This new ELISA allows determination of the concentration of apoB-48 in normolipidemic plasma.