Bone is a highly vascularized tissue. However, despite the importance of appropriate circulationfor bone health, regulation of bone blood flow remains poorly understood. Invasive animalstudies suggest that the sympathetic activity plays an important role in bone flow control.However, it remains unknown if bone vasculature evidences robust vasoconstriction in responseto sympathoexcitatory stimuli. Here, we characterized bone blood flow in young healthyindividuals (N=13,(4F)) in response to isometric handgrip exercise (IHE) and cold pressor test(CPT). These provide a strong stimulus for active vasoconstriction in the inactive muscle, andperhaps also in the bone. During sustained IHE to fatigue and CPT, we measured blood pressure,whole leg blood flow, and tibial perfusion using near-infrared spectroscopy. Tibia perfusion wasdetermined as oxy- and deoxy-hemoglobin. For both stimuli, tibial metabolism remainedconstant (i.e., no change in deoxyhemoglobin) and thus tibial arterial perfusion was representedby oxyhemoglobin. During IHE, oxyhemoglobin declined (beginning -0.20±1.04μM; end -1.13±3.71μM, both p<0.01) slower than whole leg blood flow (beginning -0.85±1.02cm/s; end -2.72±1.64cm/s, both =p<0.01). However, during CPT, both oxyhemoglobin (beginning -0.46 ±1.43μM; end -0.60±1.59μM, both p<0.01) and whole leg blood flow (beginning -1.52±1.63 cm/s;end -0.69±1.51cm/s, both p<0.01) declined with a similar time course, even though themagnitudes of decline were smaller than during IHE. These responses are likely due the differenttime courses of sympathetically mediated vasoconstriction in bone and muscle. These resultsindicate that sympathetic innervation of the bone vasculature serves a functional role in thecontrol of flow in young healthy individuals.

中文翻译：

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人体骨血流调节机制

骨是一种高度血管化的组织。然而，尽管适当的循环对骨骼健康很重要，但对骨骼血流的调节仍然知之甚少。侵入性动物研究表明，交感神经活动在骨流量控制中起重要作用。然而，尚不清楚骨脉管系统是否证明对交感神经兴奋性刺激有强烈的血管收缩作用。在这里，我们表征了年轻健康个体 (N=13,(4F)) 对等长握力运动 (IHE) 和冷加压试验 (CPT) 的反应。这些为不活动的肌肉中的活跃血管收缩提供了强烈的刺激，也许在骨骼中也是如此。在持续 IHE 到疲劳和 CPT 期间，我们使用近红外光谱测量了血压、全腿血流和胫骨灌注。胫骨灌注被确定为氧和脱氧血红蛋白。对于这两种刺激，胫骨代谢保持恒定（即脱氧血红蛋白没有变化），因此胫骨动脉灌注以氧合血红蛋白为代表。在 IHE 期间，氧合血红蛋白下降（开始 -0.20±1.04μM；结束 -1.13±3.71μM，均 p<0.01）慢于全腿血流量（开始 -0.85±1.02cm/s；结束 -2.72±1.64cm/s，两者=p<0.01）。然而，在 CPT 期间，氧合血红蛋白（开始 -0.46 ±1.43μM；结束 -0.60±1.59μM，均 p<0.01）和全腿血流量（开始 -1.52±1.63 cm/s；结束 -0.69±1.51cm/s , p<0.01) 以相似的时间过程下降，尽管下降的幅度小于 IHE 期间。这些反应可能是由于交感神经介导的骨骼和肌肉血管收缩的不同时间过程。