Determination of Immuno-Reactive Rabbit Apolipoprotein B-48 in Serum by ELISA

Apolipoprotein B-48 (apoB-48) is produced by the small intestine, is associated with chylomicrons, and appears to be a suitable marker for clinical studies of postprandial dynamics of lipoproteins. It is also associated with cardiovascular risk factors. We have developed an assay system to quantify immuno-reactive apoB-48 in rabbit serum or plasma. A microtiter-plate was coated with monoclonal antibody raised against human apoB-48 C-terminal specific decapeptide that has high homology to the rabbit C-terminal sequence. Appropriate ELISA standard curves were obtained using apoB-48 extracted from rabbit serum by immuno-affinity chromatography. No cross-reactivity was found with apoB-100 in western blot analyses. Intra- and inter-assay CVs were less than 3%. Recovery of rabbit apoB-48 spiked in serum was within 93.4-105%. ApoB-48 levels in healthy controls rabbits fed a normal diet were within the range of 0.903-1.09 microg/ml (mean +/- SD: 1.03 +/- 0.084 microg/ml). In healthy animals, the blood apoB-48 level was markedly increased by a high fat diet and in the postprandial state in parallel with serum triglyceride. Ezetimibe, cholesterol absorption inhibitor, given orally to rabbits fed on a high fat diet blocked further increase of blood levels of apoB-48 and triglyceride. This method for measuring apoB-48 using the monoclonal antibody is simple, reliable, and suitable for routine analyses.