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目的研究不同时段间断性 45°头高位对抗措施 (intermittent +45°head up tilt,IHUT)对尾吊大鼠承重骨的影响。方法SD雄性大鼠 2 8只 ,按体重配对后随机等分为 :对照组 (C) ,悬吊组 (S) ,2h头高位组 (H2 )和 4h头高位组 (H4) ,每组 7只。在尾吊大鼠模型模拟失重的基础上 ,H组大鼠每日分别给予 2h、4hIHUT。利用物理测量和 3点弯曲实验 ,观察了 3wkIHUT对尾吊大鼠股骨生长、生物力学特性的影响。结果S、H各组大鼠股骨重量、灰分、直径和密度 (H2组除外 )均较C组大鼠显著下降 (P <0 .0 1或P <0 .0 5) ;与S组比较 ,H2组大鼠的股骨直径 (P <0 .0 5)和密度 (P <0 .0 1 )显著改善。生物力学测定结果显示S组大鼠股骨的强度和刚度显著降低 (P <0 .0 1 ) ;与S组大鼠相比 ,H2组大鼠弹性载荷显著提高 (P <0 .0 5) ,H4组弹性载荷、最大载荷、韧性系数显著恢复 (P <0 .0 1或P <0 .0 5)。结论IHUT对尾吊大鼠的承重骨的力学特性改善明显 ,延长作用时间可促进生物力学性能的提高。
Objective To study the effect of intermittent + 45 ° head up tilt (IHUT) at intermittent 45 ° on the weight-bearing bone in tail-suspended rats at different time points. Methods Male Sprague-Dawley rats were randomly divided into control group (C), suspension group (S), 2h head-high group (H2) and 4h head-height group only. On the basis of simulated weightlessness in tail-suspended rat model, rats in group H were given 2h and 4hIHUT respectively. The effect of 3wkIHUT on the femoral growth and biomechanical properties of tail-suspended rats was observed by physical measurements and 3-point bending test. Results Compared with group C, the femoral weight, ash, diameter and density (except H2 group) in S and H groups decreased significantly (P <0.01 or P <0.05) The femoral diameter (P <0.05) and density (P <0.01) in H2 group were significantly improved. Biomechanical measurements showed that the strength and stiffness of the femur of rats in S group were significantly decreased (P <0.01). Compared with S rats, the elastic load of rats in H2 group was significantly increased (P <0.05) The elastic load, maximum load and toughness of H4 group were significantly recovered (P <0.01 or P <0.05). Conclusion IHUT can improve the mechanical properties of the bearing bone in tail-suspended rats, and prolong the action time to improve the biomechanical properties.