卵巢切除大鼠血清三种骨钙素变化与骨丢失

Changes of serum osteocalcin and bone loss in ovariectomized rats

本实验以卵巢切除（ＯＶＸ）大鼠为动物模型，利用血骨钙素（Ｏｓｔｅｏｃａｌｃｉｎ，ＯＣ）能够与羟磷灰石结合的特性，研究了ＯＶＸ大鼠血清中总ＯＣ，与羟磷灰石具有高亲合力ＯＣ（结合型ＯＣ）和低亲合力ＯＣ（游离型ＯＣ）水平随时间变化的特点及与骨丢失的关系。实验结果显示，ＯＶＸ１５天大鼠血中总ＯＣ，结合型ＯＣ和游离型ＯＣ均显著增加，第３腰椎（Ｌ３）矿盐密度显著降低。ＯＶＸ３０天大鼠血清总ＯＣ水平无明显改变，但游离型ＯＣ水平显著增加，结合型ＯＣ水平显著降低，Ｌ３矿盐密度显著降低。ＯＶＸ６０天大鼠血清总ＯＣ和游离型ＯＣ显著增加，Ｌ３矿盐密度显著降低，但结合型ＯＣ无明显改变。实验结果提示，ＯＶＸ大鼠骨盐丢失与骨内ＯＣ羧化作用降低或羧化作用与ＯＣ合成增加间脱偶联有关。血总ＯＣ可用于评价骨转换型的指标，血结合型ＯＣ可用于骨形成的指标，而游离型ＯＣ可用于判断骨丢失的指标。

Ovariectomy has a proven pronounced effect on bone mass. Osteocalcin(OC) can be bound to hydroxyapatite. The aim of the study was to investigate the relationship between changes of three sorts of OC in serum and bone loss in rats ovariectomized for different periods. We measured serum total OC(OC(total)),OC with high affinity for hydroxyapatite (OC(bound)),OC with low affinity for hydroxyapatite (OC(free)), and bone mineral density in the third lumbar vertebra (L3). The results revealed that serum OC(total),OC(free) and OC(bound) significantly increased and bone mineral density in significantly decreased in rats ovariectomized for 15 days. Serum OC(total) had no change, but OC(free) significantly increased, OC(bound) and bone mineral density in L3 signlficantly decreased in rats ovariectomized for 30 days. Serum OC(total) and OC(free) significantly increased, serum OC(bround) had no change, and bone mineral density in L3 significantly reduced in rats ovariectomized for 60 days. The results suggest that the decrease in carboxylation effect on OC or uncoupling between increased secretion of OC by osteoblasts and carboxylation effect on OC in bones may be one of the important reasons for bone loss in ovariectomized rats. The possibility is put forward that serum OC(total) levels may be a marker of bone turnover, OC(bound) may be a marker of bone formation, and OC(free) may be a marker of bone loss.