The effects of simulated weightlessness on bone maturation.
The effects of simulated weightlessness on bone maturation.
复制标题
模拟失重对骨骼成熟的影响。
作者：
D. Bikle;B. Halloran;C. M. Cone;R. Globus;E. Morey
在我们先前的研究表明,提高增长的后肢大鼠2周的结果在一个临时停止的后肢骨骼生长和瞬态的血清水平下降1,25-dihydroxyvitamin d来确定这样的骨骼卸货也阻碍骨骼的成熟,如维生素D-deprived动物,我们分离,密度从大鼠胫骨的后肢可以提高到15天。对这些馏分进行干重、钙含量、钙和脯氨酸摄取分析。密度最大的部分（分数4）矿化程度最高（钙与干重之比），占对照胫骨总干重的82%。去除胫骨前24 h体内给药的[3H]脯氨酸的总掺入量均匀分布在所有馏分中，尽管当归一化到干重时，密度最小的馏分（馏分1）的掺入量最高。45Ca的总掺入量在组分4中最高，但按干重归一化后在组分3中最高。随着骨骼的卸载，骨和45Ca掺入比例在分数4中降低，而在低密度分数中比例增加。[3H]各馏分脯氨酸掺入量均下降。这些效应在卸载10天后达到最大，并在10天后恢复到控制值。我们得出结论，骨骼卸载暂时减少了生长大鼠的骨形成和延迟矿化，从而导致成熟骨的减少。
In earlier studies we showed that elevating the hind limbs of growing rats for up to 2 weeks results in a temporary cessation of bone growth in the hind limbs and a transient fall in the serum levels of 1,25-dihydroxyvitamin D. To determine whether such skeletal unloading also retards the maturation of bone, as seen in vitamin D-deprived animals, we fractionated by density the tibiae from rats whose hind limbs had been elevated for up to 15 days. These fractions were analyzed for dry weight, calcium content, and calcium and proline uptake. The most dense fraction (fraction 4) had the highest degree of mineralization (ratio of calcium to dry weight) and comprised 82% of the total dry weight of the control tibiae. The total incorporation of [3H]proline administered in vivo 24 h before removing the tibiae was evenly distributed among all of the fractions, although it was highest in the least dense fraction (fraction 1) when normalized to dry weight. Total incorporation of 45Ca was highest in fraction 4, although when normalized to dry weight it was highest in fraction 3. With skeletal unloading, the proportions of bone and 45Ca incorporation in fraction 4 decreased, while the proportions in less dense fractions increased. [3H]Proline incorporation fell in all fractions. These effects were maximal after 10 days of unloading and returned toward the control values after that time. We conclude that skeletal unloading transiently reduced bone formation and retarded mineralization in the growing rat, which resulted in a decrease in mature bone.