Leuenberger U, Sinoway L, Gubin S, Gaul L, Davis D, Zelis R
Department of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033.
J Appl Physiol (1985). 1993 Aug;75(2):668-74. doi: 10.1152/jappl.1993.75.2.668.
During dynamic exercise, blood flow to exercising muscle is closely matched to metabolic demands. This is made possible by metabolic vasodilation, vasoconstriction in inactive vascular beds, and a rise in cardiac output. The sympathetic nervous system plays an important role in regulating this exercise response. In this study, we used steady-state infusions of tritiated norepinephrine ([3H]NE) to determine the magnitude and time course of the arterial NE spillover response to sustained upright bicycle exercise at low (n = 11) and moderate-to-high (n = 14) exercise intensity (25 and 65% of maximum work load, respectively) in normal young subjects. In addition, we sought to examine whether exercise was associated with a change in NE clearance. During 30 min of low-level exercise, arterial NE spillover increased from 1.45 +/- 0.13 to 3.14 +/- 0.30 nmol.min-1 x m-2 (P < 0.01) and appeared to plateau at 20-30 min of exercise; NE clearance remained unchanged. During 20 min of moderate-to-high-intensity exercise, we found a substantial and progressive rise of arterial NE spillover from 2.15 +/- 0.27 to 13.52 +/- 1.62 nmol.min-1 x m-2 (P < 0.01). NE clearance decreased from 0.91 +/- 0.05 to 0.80 +/- 0.05 l.min-1 x m-2 (P < 0.05). These data suggest that, during dynamic exercise, sympathetic nervous system activity is related to exercise intensity, and there appears to be an interaction between the effects of exercise intensity and duration on NE spillover. In addition, at moderate-to-high exercise intensity, a small decrease of NE clearance contributes to the rise in plasma NE.
在动态运动过程中，流向运动肌肉的血流量与代谢需求紧密匹配。这通过代谢性血管舒张、非活动血管床的血管收缩以及心输出量的增加得以实现。交感神经系统在调节这种运动反应中起重要作用。在本研究中，我们使用氚标记去甲肾上腺素（[³H]NE）的稳态输注来确定正常年轻受试者在低强度（n = 11）和中高强度（n = 14）运动强度（分别为最大工作负荷的25%和65%）下进行持续直立自行车运动时，动脉NE溢出反应的幅度和时间进程。此外，我们试图研究运动是否与NE清除率的变化有关。在30分钟的低强度运动期间，动脉NE溢出从1.45±0.13增加到3.14±0.30 nmol·min⁻¹·m⁻²（P < 0.01），并且在运动20 - 30分钟时似乎达到平台期；NE清除率保持不变。在20分钟的中高强度运动期间，我们发现动脉NE溢出从2.15±0.27大幅且持续上升至13.52±1.62 nmol·min⁻¹·m⁻²（P < 0.01）。NE清除率从0.91±0.05降至0.80±0.05 l·min⁻¹·m⁻²（P < 0.05）。这些数据表明，在动态运动期间，交感神经系统活动与运动强度相关，并且运动强度和持续时间对NE溢出的影响之间似乎存在相互作用。此外，在中高强度运动时，NE清除率的小幅下降有助于血浆NE的升高。
