| Co-Investigator(Kenkyū-buntansha) |
OZAKI Miho Nagasaki University, School of Dentistry Research Fellow, 歯学部, 教務職員 (50191341)
KOBAYASHI Yasuhiro Nagasaki University, School of Dentistry Research Associate, 歯学部, 助手 (20264252)
NISHISHITA Kazuhisa Nagasaki University, School of Dentistry Research Associate, 歯学部, 助手 (20237697)
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| Research Abstract |
Osteocalcin is a vitamin K-dependent, bone-specific protein that is secreted by osteoblasts. Several studies have shown that it is a sensitive and specific marker of osteoblastic activity in a variety of metabolic bone disease and may refect bone remodeling activity. However, there is some controversy regarding the significance of serum osteocalcin levels in various metabolic bone diseases. This is probably due to the immunochemical heterogeneity of circulating osteocalcin. In this study, we have focused on the N-terminal sequence of osteocalcin and raised a monoclonal antibody against its synthetic N-terminal 20-residue peptide. Using this monoclonal antibody and polyclonal antibody against C-terminal 8-residue peptide, we have developed a region specific sandowich immunoassay for rat osteocalcin, i. e. for intact osteocalcin (IOC) and N-terminal osteocalcin (NOC) , respectively. To obtain physiological data to assess the validity and sensitivity of developed immunoassays, several exp
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eriments which are known to cause alteration in bone turnover, were performed. When the developmental changes in serum levels of IOC and NOC were examined in 8,15,30, and 60 weeks old rats, IOC and NOC decreased in an age-dependent manner, in agreement with decrease of bone turnover rate. In the rats fed on low Ca diet where bone resorption had been accelarated, a significant increases of IOC and NOC were observed, however, the change of NOC was more evident than of IOC.In addition, an acute effect of eel calcitonin administration on serum osteocalcin levels were examined in the rats fed on low Ca diet. After the injection of calcitonin, a transient decrease in serum NOC level was observed, whereas serum IOC level did not change. Further, there were significant correlation between serum NOC level and urinary excretion of collagen crosslinks, indices for bone resorption. These results suggest that serum levels of IOC and NOC might be used as a marker for bone formation and bone resorption respectivery. This newly developed region specific enzyme immunoassay for rat osteocalcin molecules may give useful information on bone metabolism in rats, commonly used in the laboratory investigations. Less
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