Hirano T, Burr D B, Turner C H, Sato M, Cain R L, Hock J M
Department of Anatomy, Indiana University School of Medicine, Indianapolis, USA.
J Bone Miner Res. 1999 Apr;14(4):536-45. doi: 10.1359/jbmr.1999.14.4.536.
Intermittent administration of parathyroid hormone (PTH) has an anabolic effect in cancellous bone of osteoporotic humans. However, the effect of PTH on cortical bone with Haversian remodeling remains controversial. The aim of this study was to determine the effects of biosynthetic human PTH(1-34) on the histology and mechanical properties of cortical bone in rabbits, which exhibit Haversian remodeling. Mature New Zealand white rabbits were treated with once daily injections of vehicle, or PTH(1-34), LY333334, at 10 micrograms/kg/day or 40 micrograms/kg/day for 140 days. Body weight in rabbits treated with PTH did not change significantly over the experimental period. Serum calcium and phosphate were within the normal range, but a 1 mg/ml increase in serum calcium was observed in rabbits given the higher dose of PTH. Histomorphometry of cortical bone in the midshaft of the tibia showed significant increases in periosteal and endocortical bone formation in these rabbits. Intracortical bone remodeling in the tibia was activated and cortical porosity increased by PTH. Cross-sectional bone area and bone mass of the midshaft of the femur increased significantly after PTH treatment. Ultimate force, stiffness, and work to failure of the midshaft of the femur of rabbits given the 40 micrograms dose of PTH were significantly greater than those in the control group, whereas elastic modulus was significantly lower than that in the rabbits given the 10 micrograms dose of PTH, but not different from controls. In the third lumbar vertebra, PTH increased both formation and resorption without increasing cancellous bone volume. The increases in bone turnover and cortical porosity were accompanied by concurrent increases in bone at the periosteal and endocortical surfaces. The combination of these phenomena resulted in an enhancement of the ultimate stress, stiffness, and work to failure of the femur.
间歇性给予甲状旁腺激素（PTH）对骨质疏松症患者的松质骨具有合成代谢作用。然而，PTH对具有哈弗斯改建的皮质骨的影响仍存在争议。本研究的目的是确定生物合成的人PTH（1-34）对表现出哈弗斯改建的兔皮质骨组织学和力学性能的影响。将成年新西兰白兔每天注射一次赋形剂、10微克/千克/天或40微克/千克/天的PTH（1-34）或LY333334，持续140天。在实验期间，接受PTH治疗的兔子体重没有显著变化。血清钙和磷在正常范围内，但给予较高剂量PTH的兔子血清钙增加了1毫克/毫升。胫骨中段皮质骨的组织形态计量学显示，这些兔子的骨膜和内皮质骨形成显著增加。PTH激活了胫骨的皮质内骨重塑并增加了皮质孔隙率。PTH治疗后，股骨中段的横截面骨面积和骨量显著增加。给予40微克剂量PTH的兔子股骨中段的极限力、刚度和破坏功显著大于对照组，而弹性模量显著低于给予10微克剂量PTH的兔子，但与对照组无差异。在第三腰椎，PTH增加了骨形成和骨吸收，但未增加松质骨体积。骨转换和皮质孔隙率的增加伴随着骨膜和内皮质表面骨量的同时增加。这些现象的综合作用导致股骨的极限应力、刚度和破坏功增强。
