Human Retinol Binding Protein (RBP) Serum EIA Kit

Retinol Binding Protein (RBP) Immunoassay Kit is designed to measure RBP levels in serum, EDTA and heparin plasma. This kit uses native human RBP as a standard, the concentration of which has been established via amino acid analysis. Standards or diluted samples are pipetted into a microtiter plate coated and RBP-peroxidase conjugate is added. The binding reaction is initiated by addition of a RBP-specific rabbit polyclonal antibody. After a 60-minute incubation, the plate is washed and TMB substrate solution added to each well. After 15 minutes the intensity of the generated signal is read at 450 nm in a microtiter plate reader.
Retinol binding protein (RBP) is from a family of structurally related proteins that bind small hydrophobic molecules such as bile pigments, steroids, odorants, etc. RBP is a highly conserved 21 kDa single-chain glycoprotein, consisting of 182 amino acids with 3 disulfide bonds, that has a hydrophobic pocket which binds retinol (vitamin A). RBP binds retinol in a 1:1 stoichiometry, which serves to not only solubilize retinol but also protect it from oxidation. When in serum, the majority of RBP bound with retinol is reversibly complexed with transthyretin. This complex transports retinol to specific receptors of various tissues in the body. Vitamin A status is reflected by serum concentration as it is homeostatically controlled and does not fall until stores are dramatically reduced. RBP has been shown to be a useful surrogate marker for retinol because of the correlation between retinol and RBP in serum, which implies that RBP may be used to monitor vitamin A deficiency (VAD). The WHO has estimated that 250 million children have moderate to severe VAD due to lack of adequate nutrition, and the rising cost of food staples around the world further exacerbates this problem. In addition to nutritional deficiencies, infectious stresses have been shown to depress retinol concentrations and individuals with diseases such as cystic fibrosis and HIV-1 also run the risk of VAD due to the infectious stresses that contribute to the disease. Modulating RBP4 levels may lead to new strategies in treating type 2 diabetes.