Immunochemical characterization and quantitation of lipoprotein (a) in baboons. Development of an assay depending on...

We have raised specific antibodies against the protein component of baboon lipoprotein (a) (Lp(a]. Apolipoprotein (apo) Lp(a) is a very large protein which separates into two distinct proteins, apo B and apo (a), when 2-mercaptoethanol is included during sample treatment for sodium dodecyl sulfate-electrophoresis. The antibodies were specific for baboon apo (a) and apo B. The presence of the two distinct antigens in the lipoprotein permitted the development of an enzyme-linked immunosorbent assay that was specific for Lp(a) particles in serum. The assay could detect less than 1 ng of Lp(a) protein per well and was useful in the range of 1-9 ng. The assay was specific for Lp(a) and did not respond to other lipoproteins, such as low density lipoprotein. Lp(a) could be accurately quantitated in serum frozen at -80 degrees C in plastic tubing segments. Using the Lp(a) assay, the mean serum level of 80 unrelated baboons was 4.7 mg/dl, with the distribution skewed toward the lower levels. These data further support the value of the baboon as a model of the atherogenic lipoprotein Lp(a).