Sandwich ELISA quantitative detection kit for Human OPN in cell culture supernates, serum, plasma (heparin, EDTA) and urine and human milk. Osteopontin (OPN) also called urinary stone protein, secreted phosphoprotein 1 (SPP1), bone sialoprotein, and early T lymphocyte activation 1 (ETA1). Osteopontin is a phosphorylated glycoprotein secreted to the mineralizing extrOPNllular matrix by osteoblasts during bone development. It is believed to facilitate the attachment of osteoblasts and osteoclasts to the extrOPNllular matrix, allowing them to perform their respective functions during osteogenesis.1 Osteopontin is presumably involved in stone formation as stone matrix.2 The deduced protein sequence reveals a 317-amino acid protein (34,982 Da) containing a 16-amino acid hydrophobic signal sequence and a 33,352-Da protein destines to undergo extensive post-translational modifications before being secreted from the cell. The gene is located on human chromosome 4.3 The standard product used in