Description
Principle of the assay: This assay employs a two-site sandwich ELISA to quantitative ASP in Rat serum, plasma. An antibody specific for ASP has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any ASP present is bound by the immobilized antibody. After removing any unbound substances, a biotin - conjugated antibody specific for ASP is added to the wells. After washing, Streptavidin conjugated Horseradish Peroxidase (HRP) is added to the wells. Following a wash to remove any unbound avidin-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of ASP bound in the initial step. The color development is stopped and the intensity of the color is measured.
Background: Complement 3 (C3) through its interaction with factors B and D (adipsin) generates C3a. In the human body, C3a is rapidily cleaved by carboxypeptidase B or carbxyopeptidase N, that remove the carboxyl-terminal arginine to generate C3adesArg. Thus, most of plasmatic C3a is present in C3adesArg form. C3adesArg is more commonly named ASP or acylation-stimulating-protein due to its marked stimulating action on triacylglycerol synthesis in human adipocytes and skin fibroblasts. ASP is also known for its augmentation of glucose transport and inhibiting action on hormone-sensitive lipase. Because of these actions, it is linked to the pathogenesis of obesity, having been demonstrated to be present at increased levels in patients with obesity, diabetes mellitus type 2 and coronary artery disease. ASP ligates a specific receptor named C5L2 which is coupled with a G-protein. The view of C3a/C3adesArg as an acylation stimulating activity is not universally accepted. The evidence is discussed in a recent review