大鼠骨生物学指标的月龄特征

Age-related changes of bone biological indices in rats

目的 观察大鼠骨密度、骨生物力学和骨矿元素含量的月龄特征和变化规律。 方法采用固体物理密度测试方法测量大鼠股骨和腰椎标本骨密度和体积,三点弯曲试验和压缩试验分别测试股骨最大抗弯载荷和腰椎最大抗压载荷,自动生化分析仪测试骨组织浸出液中钙、磷和镁含量,计算单位体积含量。结果 骨密度峰值区间为7-12月龄,股骨平均密度峰值为1.429(雌性)和1.399g/cm3(雄性),腰椎平均密度峰值为1.207(雌性)和1.204g/cm3(雄性)。随后开始减低,12-16月龄阶段股骨密度减低明显,而腰椎出现在16-18月龄,18月龄以后骨密度变化不大。股骨抗弯强度雌性大鼠增加至12月龄(198.29N),而雄性大鼠可持续至18月龄(323.2N),随后逐渐减低至24月龄的211和157N。腰椎抗压能力增强至12月龄的252-263N后逐渐减低,24月龄时维持138-149N。股骨和腰椎中Ca和P的含量呈7月龄为峰值的双相变化,高龄阶段Ca含量小幅减低。镁含量随年龄变化不大。结论 骨生物学指标呈阶段性特征,7-12月龄阶段骨量相对稳定,而力学性能不断改善。12月龄后骨量开始丢失,并可能存在一个短暂快速丢失期。18月龄以后丢失减缓,骨量相对稳定。

Objective To study the age-related changes in density,biomechanics and mineral contents of rat femur and lumbar vertebrae. Methods The density and volume of rat femur and lumbar vertebrae (L4) were measured by Archimedes principle. The mechanical property of femur and vertebrae were evaluated by the three-point bending test and the compression test separately. Ca, Mg and P levels in bone extract were analyzed and cal-culated by biochemical methods. Results The bone density increased with age, and the peaks appeared in 7-12 months of age, followed by a rapid decrease at 12-16 months of age for femur and after 16 months of age for lumbar vertebrae. The mechanical strength increaced to 252-263 and 198N at the age of 12 months for lumbar vertebrae and femur of females, respectively, then slowed down. The levels of Ca and P showed diphasetransition with age, and the peak appeared at 7 months of age, while the Mg level was constant. Conclusion The biological indices of skeleton vary diphasically with age. The bone density is stabilized of 7-12 months of age with improvement of its mechanical property; thereafter, the bone loss occurs possibly in a rapid and transient way at beginning, and slows down after 18 months of age.