Hagino H, Raab D M, Kimmel D B, Akhter M P, Recker R R
Center for Hard Tissue Research, Creighton University, Omaha, Nebraska.
J Bone Miner Res. 1993 Mar;8(3):347-57. doi: 10.1002/jbmr.5650080312.
This study was undertaken to find whether the bone response to increased external loading (EL) of the tibia in rats is affected by estrogen depletion. Female Sprague-Dawley rats 6 months were randomly assigned to four groups of 10 each: sham ovariectomy without loading (Shm-XL), ovariectomy without loading (OVX-XL), sham ovariectomy with external loading (Shm-EL), and ovariectomy with external loading (OVX-EL). In vivo external loading by a four-point bending device was initiated 4 weeks after surgery. The right lower leg of each EL rat was loaded at 31.4 +/- 0.2 N for 36 cycles at 2 Hz every other day for 21 days (11 loading days). Mean in vivo induced strain was 1305 microstrain (mu epsilon) for Shm-EL rats and 1280 mu epsilon for OVX-EL rats. With external loading of the tibia, periosteal bone formation rose equally in Shm and OVX rats. Woven bone was present around the tibia or fibula in 60% of the loaded rats and none of the control rats. No loading response occurred either at the endocortical surface or in the cancellous bone of the proximal tibial metaphysis. After OVX, cancellous bone area in the proximal metaphysis declined and formation surface rose compared to Shm rats. Although periosteal and endocortical bone formation rose after OVX, no cortical bone loss occurred. We conclude that ovariectomy and attendant loss of endogenous estrogen do not change the cortical bone response to an external load of about 1300 mu epsilon in rats. However, these results may not predict the cortical bone response to loading in animals with Haversian remodeling that display estrogen-related loss of cortical bone.
本研究旨在探究大鼠胫骨对外加负荷增加的骨反应是否受雌激素缺乏的影响。将6个月大的雌性斯普拉格 - 道利大鼠随机分为四组，每组10只：假去卵巢未加载组（Shm - XL）、去卵巢未加载组（OVX - XL）、假去卵巢外加负荷组（Shm - EL）和去卵巢外加负荷组（OVX - EL）。术后4周开始用四点弯曲装置进行体内外加负荷。每只EL大鼠的右小腿每隔一天以31.4±0.2 N的力加载36个周期，频率为2 Hz，持续21天（共11个加载日）。Shm - EL大鼠的平均体内诱导应变是1305微应变（με），OVX - EL大鼠为1280 με。对胫骨施加外加负荷后，Shm组和OVX组大鼠的骨膜骨形成均等量增加。60%的加载大鼠胫骨或腓骨周围出现编织骨，而对照组大鼠均未出现。在胫骨近端干骺端的内皮质表面或松质骨中均未出现加载反应。去卵巢后，与Shm组大鼠相比，近端干骺端的松质骨面积减少，形成表面增加。虽然去卵巢后骨膜和内皮质骨形成增加，但未发生皮质骨丢失。我们得出结论，去卵巢及随之而来的内源性雌激素丧失不会改变大鼠对约1300 με外加负荷的皮质骨反应。然而，这些结果可能无法预测具有哈弗斯改建且显示与雌激素相关的皮质骨丢失的动物对加载的皮质骨反应。
