Objective To study the effect of once-weekly injection of recombinant human parathyroid hormone rhPTH(1-34) on the healing of bone fracture in rats.Methods Fifty male 3-month old SD rats were used in this study to produce unilateral tibial fracture and received internal fixation with a Kirschner needle.Based on the dose and frequency of rhPTH (1-34) injection, the rats were randomly divided into five groups (n=10 each) as follows: subcutaneous injec-tions of saline, and rhPTH in a dose of 10, 20, 10, and 20 μg/kg/d.After 4 weeks of treatment, the rats were euthana-tized and the fractured tibia were assessed by X-ray, dual energy X-ray absorptiometry ( DXA) ,micro-computed tomography ( microCT) and three-point bending test.Results The fracture healing in the 20μg/kg/w group was better than the saline group.The fracture healing in the 20μg/kg/w group was as well as the 10 μg/kg/dgroup.The BMD of 20μg/kg/w group was 26.2%higher than the saline group.The mineralized callus volume in the 20μg/kg/w group was 51.4%higher than the saline group.The total callus volume in the 20μg/kg/w group was 21.6%higher than the saline group.The ultimate load of the 20 μg/kg/w group was 29.3% higher than the saline group.There was no significant difference between the 20 μg/kg/w group and 10 μg/kg/d group in BMD, bone micro-architecture, and biomechanical strength ( P >0.05 ) . Conclusions Once weekly injection of rhPTH (1-34)can promote the bone fracture healing.%目的：观察每周单次皮下注射甲状旁腺激素rhPTH（1－34）促进大鼠骨折愈合的效果。方法50只3月龄雄性SD大鼠左侧胫骨骨折，克氏针内固定术后，根据皮下注射rhPTH（1－34）的剂量及频次，随机分为5组（n＝10／组）：每周10、20μg／kg组；每日10、20μg／kg组；每周皮下注射等量（500μL）生理盐水作为对照组。治疗4周后处死取材，分别行小动物X线、双能X线、micro-CT及三点弯曲生物力学实验检测骨折愈合情况。结果无论每周或每日皮下注射rhPTH（1－34）骨密度均高于对照组（P＜0.05）；每周20μg／kg组骨折愈合效果好于对照组，其中rhPTH（1－34）每周20μg／kg组在骨密度、矿化的骨痂体积、骨痂总体积、矿化的骨痂体积占骨痂总体积百分数、最大载荷方面分别比对照组高26.2％、51.4％、21.6％、24.5％、29.3％。每周20μg／kg、每日10μg／kg及每日20μg／kg组的最大载荷均高于对照组（ P＜0.01）；每周20μg／kg组骨密度、骨微结构、力学强度均与每日10μg／kg组无统计学差异（P＞0.05）。结论每周皮下注射甲状旁腺激素（rhPTH1-34）（10、20μg／kg）可以促进骨折愈合，但相同单次剂量，每日皮下注射的效果仍优于每周皮下效果。
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