González-Alonso José, Olsen David B, Saltin Bengt
Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Denmark.
Circ Res. 2002 Nov 29;91(11):1046-55. doi: 10.1161/01.res.0000044939.73286.e2.
Blood flow to contracting skeletal muscle is tightly coupled to the oxygenation state of hemoglobin. To investigate if ATP could be a signal by which the erythrocyte contributes to the regulation of skeletal muscle blood flow and oxygen (O2) delivery, we measured circulating ATP in 8 young subjects during incremental one-legged knee-extensor exercise under conditions of normoxia, hypoxia, hyperoxia, and CO+normoxia, which produced reciprocal alterations in arterial O2 content and thigh blood flow (TBF), but equal thigh O2 delivery and thigh O2 uptake. With increasing exercise intensity, TBF, thigh vascular conductance (TVC), and femoral venous plasma [ATP] augmented significantly (P<0.05) in all conditions. However, with hypoxia, TBF, TVC, and femoral venous plasma [ATP] were (P<0.05) or tended (P=0.14) to be elevated compared with normoxia, whereas with hyperoxia they tended to be reduced. In CO+normoxia, where femoral venous O2Hb and (O2+CO)Hb were augmented compared with hypoxia despite equal arterial deoxygenation, TBF and TVC were elevated, whereas venous [ATP] was markedly reduced. At peak exercise, venous [ATP] in exercising and nonexercising limbs was tightly correlated to alterations in venous (O2+CO)Hb (r2=0.93 to 0.96; P<0.01). Intrafemoral artery infusion of ATP at rest in normoxia (n=5) evoked similar increases in TBF and TVC than those observed during exercise. Our results in humans support the hypothesis that the erythrocyte functions as an O2 sensor, contributing to the regulation of skeletal muscle blood flow and O2 delivery, by releasing ATP depending on the number of unoccupied O2 binding sites in the hemoglobin molecule.
流向收缩骨骼肌的血流量与血红蛋白的氧合状态紧密相关。为了研究ATP是否可能是红细胞参与调节骨骼肌血流量和氧气（O₂）输送的信号，我们在常氧、低氧、高氧和一氧化碳 + 常氧条件下，对8名年轻受试者进行递增式单腿伸膝运动时测量了循环ATP水平，这些条件会使动脉血氧含量和大腿血流量（TBF）产生相反变化，但大腿氧气输送量和大腿氧气摄取量相等。随着运动强度增加，在所有条件下TBF、大腿血管传导率（TVC）和股静脉血浆[ATP]均显著增加（P<0.05）。然而，与常氧相比，低氧时TBF、TVC和股静脉血浆[ATP]升高（P<0.05）或有升高趋势（P = 0.14），而高氧时它们有降低趋势。在一氧化碳 + 常氧条件下，尽管动脉脱氧程度相同，但与低氧相比股静脉O₂Hb和（O₂ + CO）Hb增加，TBF和TVC升高，而静脉[ATP]显著降低。在运动峰值时，运动和未运动肢体的静脉[ATP]与静脉（O₂ + CO）Hb的变化紧密相关（r² = 0.93至0.96；P<0.01）。在常氧状态下静息时股动脉内注入ATP（n = 5）引起的TBF和TVC增加与运动时观察到的相似。我们在人体中的研究结果支持以下假设：红细胞作为一个氧传感器，通过根据血红蛋白分子中未占据的氧结合位点数量释放ATP，参与调节骨骼肌血流量和氧气输送。
