The Osteopontin ELISA is a solid-phase sandwich ELISA that uses two highly specific antibodies for human, mouse or rat osteopontin (OPN) protein; one of the antibodies is precoated onto the osteopontin ELISA plate and the other is HRP-conjugated. The osteopontin ELISA kit can be used to measure soluble human, mouse or rat OPN protein in EDTA-plasma, cell culture supernatant or urine.
OPN is a calcium-binding glycosylated phosphoprotein secreted by many cell types, including osteoblasts, kidney tubule cells, macrophages, activated T cells and vascular smooth muscle cells. It is also known as Spp-1, Apl-1, BNSP, bone sialoprotein 1, ETA-1 and minopontin. OPN molecular weight varies within a range of 44-66 kDa depending on the protein's level of glycosylation and phosphorylation. OPN contains an Arg-Gly-Asp (RGD) amino acid motif that is also found in other extracellular proteins that bind members of the integrin family of cell-surface receptors. A variety of OPN isoforms exists within the cell and is produced by differential splicing, post-translational modification and proteolytic cleavage.