The osteocalcin is a marker of bone metabolism on periodontal disease during of bone resorption

建立了N-末端骨钙素(N-OC)的特异性免疫分析系统，用于检测体外破骨细胞降解的骨中是否释放骨钙素分子，作为一种新的骨吸收测量方法。该检测系统采用针对骨钙素前20个N端残基的单抗作为固相，针对这些残基的多克隆抗体作为酶结合物。该检测系统还能检测到人骨钙素分子被胰酶或组织蛋白酶D降解时形成的骨钙素的N末端部分。使用这种N-OC测定方法，我们测量了这些培养上清液中的骨钙素含量。在破骨细胞性骨吸收过程中，培养液中主要是N末端骨钙素增加，同时完整的骨钙素水平略有增加。在破骨细胞性骨吸收刺激物IL-1b和IL-6存在下，N-末端骨钙素水平较无刺激物时增加1.5倍。相反，在破骨细胞性骨吸收的抑制剂双膦酸盐(YM175)或组织蛋白酶D抑制剂(E-)的存在下，N-末端骨钙素的释放减少。这些结果提示，破骨细胞性骨吸收过程中释放的骨钙素片段和N端骨钙素的检测可能为体外骨吸收提供有用的指标。

A specific immunoassay system for N-terminal osteocalcin (N-OC) was developed to determine if osteocalcin molecules are released from bone degraded by osteoclasts in vitro as a novel method for measuring bone resorption. The assay system employs a monoclonal antibody to the first 20 N-terminal residues of osteocalcin as the solid phase and polyclonal antibodies against these same residues as an enzyme conjugate. This assay system could also detect N-terminal portion of osteocalcin, formed during the degradation of the human osteocalcin molecule by trypsin or cathepsin D.We isolated osteoclasts from human alveolar bone, and cultured them on human bone slices. Using this N-OC assay method, we measured the osteocalcin content in the media from these cultures. Predominantly N-terminal osteocalcin increased in the culture medium, along with a slight increase in the level of intact osteocalcin, during osteoclastic bone resorption. In the presence of IL-1b and IL-6, stimulators of osteoclastic bone resorption, the level of N-terminal osteocalcin increased by 1.5 fold compared with that in the absence of the stimulators. On the contrary, in the presence of bisphosphonate (YM175) or a cathepsin D inhibitor (E-64), inhibitors of osteoclastic bone resorption, the release of N-terminal osteocalcin decreased. These results suggests that the fragments of osteocalcin released during osteoclastic bone resorption and the detection of N-terminal osteocalcin may provide a useful index for bone resorption in vitro.