Kasra M, Vanin C M, MacLusky N J, Casper R F, Grynpas M D
Centre for Biomaterials, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada.
J Orthop Res. 1997 Jan;15(1):118-23. doi: 10.1002/jor.1100150117.
The purpose of this study was to examine the effects of estrogen replacement, in concert with three different progestin regimens, on the mechanical properties of rat femoral cortical bone. Ninety-two 11-month-old female Sprague-Dawley rats were randomly divided into six groups and were treated for a duration of 6 months. Group-1 rats were intact controls, group-2 rats were ovariectomized controls, and groups 3-6 were ovariectomized and given continuous doses of estrogen with 5% estradiol 17B silicone-rubber implants. Groups 4, 5, and 6 were also given different doses of progestin (norethindrone): group 4 received a continuous dose of 3 micrograms per animal per day, group 5 received a cyclic dose of 6 micrograms per animal per day for 14 days of a 28-day cycle, and group 6 received an interrupted dose of 3 micrograms per animal per day for 3 days of a 6-day cycle. Femurs from each group were mechanically tested. Bending stiffness was measured by nondestructive three-point bending tests and maximum torque capacity, by destructive torsion tests. Geometrical properties and apparent density of cortical bone were also measured. The significant differences were: the increases in elastic modulus (measured from the three-point bending stiffness) of group 5 (cyclic norethindrone) compared with those of group 2 (ovariectomized controls) and group 3 (estrogen only); the increases in the size represented by the moment of inertia, the moment of the area, and medial-lateral width of group 2 compared with those of group 5; and the increases in apparent density and decreases in moment of inertia of group 6 (interrupted norethindrone) compared with those of group 2. Cyclic or interrupted treatment of progestin along with continuous treatment of estrogen after ovariectomy likely improves material properties of cortical bone, increases its density, and reduces the size of the bone compared with ovariectomized rats.
本研究的目的是探讨雌激素替代疗法与三种不同孕激素方案协同作用对大鼠股骨皮质骨力学性能的影响。92只11月龄雌性斯普拉格-道利大鼠被随机分为6组，治疗6个月。第1组大鼠为完整对照，第2组大鼠为卵巢切除对照，第3 - 6组大鼠卵巢切除后通过植入含5% 17β - 雌二醇的硅橡胶植入物给予持续剂量的雌激素。第4、5和6组还给予不同剂量的孕激素（炔诺酮）：第4组每只动物每天接受3微克的持续剂量，第5组在28天周期的14天内每只动物每天接受6微克的周期剂量，第6组在6天周期的3天内每只动物每天接受3微克的间断剂量。对每组大鼠的股骨进行力学测试。通过无损三点弯曲试验测量弯曲刚度，通过破坏性扭转试验测量最大扭矩能力。还测量了皮质骨的几何特性和表观密度。显著差异如下：与第2组（卵巢切除对照）和第3组（仅雌激素）相比，第5组（周期炔诺酮）的弹性模量（由三点弯曲刚度测量）增加；与第5组相比，第2组以惯性矩、面积矩和内外侧宽度表示的尺寸增加；与第2组相比，第6组（间断炔诺酮）的表观密度增加，惯性矩减小。与卵巢切除大鼠相比，卵巢切除后孕激素的周期或间断治疗与雌激素的持续治疗相结合可能会改善皮质骨的材料性能，增加其密度，并减小骨的尺寸。
