Rat Gla-Osteocalcin High Sensitive EIA Kit (Cat #MK126) is a sandwich-type EIA kit of 96-well format, which uses a rat osteocalcin C-terminus-specific antibody as capture-antibody on a solid-phase plate. This antibody has a minimal cross reactivity with bovine, human and rabbit osteocalcin. An enzyme-labeled antibody (GlaOC4-30) specific to Gla-OC is used as the detection antibody, allowing this kit to detect Gla-osteocalcin with a very high sensitivity. As such, this EIA kit is sensitive enough to detect even minute levels of rat osteocalcin produced in supernatants of cells cultured in fetal calf serum-supplemented medium.
Rat Glu-Osteocalcin High Sensitive EIA Kit (Cat.# MK146) is a sandwich-type EIA kit of 96-well format, in which rat osteocalcin C terminal region recognition specific antibody is the capture antibody on a solid plate and a monoclonal antibody that is specific to the Glu residues that straddle positions 21 and 24 of osteocalcin is arranged as the detection antibody. This product makes high-sensitivity measurement of minor antigens and maintenance of stable reproducibility possible. Moreover, as it has the same capture antibody as the Rat Gla-Osteocalcin High Sensitive EIA Kit (Cat.# MK126), the kits may be used together for simultaneous Gla/Glu detection (Cat.# MK147), thereby making simultaneous monitoring of bone formation and resorption possible.
Osteocalcin, which contains two or three gamma-carboxyglutamate (Gla) residues and has a molecular weight of approximately 5,900 Daltons, is known as a vitamin K-dependent calcium-binding noncollagen protein. Specifically produced by only osteoblasts, osteocalcin has been used as one of the osteoblast markers. The rat osteocalcin consists of a total of 50 amino acids. Human, bovine, rabbit, and other species have a osteocalcin with 49 amino acids. The three glutamate residues at positions 17, 21, and 24 of the amino acid chain are carboxylated, forming a calcium pocket that allows osteocalcin to bind to bone matrix. Osteocalcin is also a hormone that plays a role in insulin regulation and in male fertility. The undercarboxylated form (ucOC), in particular, is responsible for regulation of glucose metabolism. This kit enables researchers to study the roles that both carboxylated and uncarboxylated forms of osteocalcin play in metabolic disease, male fertility and bone formation and resorption.
Osteoblasts generally produce osteocalcin with all three of its glutamate residues carboxylated (Gla-OC), affording the protein its ability to bind with bone matrix. During bone metabolism, osteocalcin is released from bone matrix through the actions of various enzymes, including one produced by osteoclasts. Most of the three glutamate residues are decarboxylated on osteocalcin (Glu-OC) when it is released into blood from bone. Therefore, osteocalcin is present in blood in both Gla and Glu forms and is made up of a wide range of molecular species, from full-length to fragmented molecules.
