Effects of 14 days of head-down tilt bed rest on cutaneous vasoconstrictor responses in humans.
Effects of 14 days of head-down tilt bed rest on cutaneous vasoconstrictor responses in humans.
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DOI：
10.1152/japplphysiol.00067.2002
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发表时间：
2003-06
影响因子：
3.3
通讯作者：
T. Wilson;M. Shibasaki;J. Cui;B. Levine;C. Crandall
中科院分区：
文献类型：
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作者：
T. Wilson;M. Shibasaki;J. Cui;B. Levine;C. Crandall
这项研究检验了头低位倾斜卧床休息 (HDBR) 会降低肾上腺素能和非肾上腺素能皮肤血管收缩反应性的假设。此外，还包括一个运动对策组，以确定卧床休息期间的运动是否可以抵消 HDBR 期间出现的任何血管收缩缺陷。 22 名受试者接受了为期 14 天的严格 6 度 HDBR 测试。这 22 名受试者中有 8 名在 HDBR 期间没有锻炼，而其中 14 名受试者每天在仰卧自行车测力计上以睡前最大心率的 75% 锻炼 90 分钟。为了评估α-肾上腺素能血管收缩剂的反应性，使用皮内微透析局部施用去甲肾上腺素（NE），同时通过微透析膜监测前臂皮肤血流（SkBF；激光多普勒血流测定法）。使用非线性回归模型确定引起 50% 皮肤血管收缩反应 (EC(50)) 的有效药物浓度以及 SkBF-NE 剂量反应曲线的最小值。此外，通过前臂和腿部的静脉小动脉反应评估 HDBR 对非肾上腺素能皮肤血管收缩的影响。无论受试者在 HDBR 期间是否运动，HDBR 均不会改变 EC(50) 或外源 NE 给药的皮肤血管收缩幅度。此外，在 HDBR 期间，HDBR 并没有改变对照组或运动组的前臂静脉小动脉反应。然而，由于腿部静脉小动脉反应，HDBR 显着降低了皮肤血管收缩的程度，并且这种反应在运动组中也同样降低。这些数据表明 HDBR 不会改变外源性 NE 给药的皮肤血管收缩反应，而 HDBR 后由于静脉小动脉反应引起的腿部皮肤血管收缩减少。目前尚不清楚下肢静脉小动脉反应减弱是否会导致卧床休息和太空飞行后体位耐受力降低。
This study tested the hypothesis that head-down tilt bed rest (HDBR) reduces adrenergic and nonadrenergic cutaneous vasoconstrictor responsiveness. Additionally, an exercise countermeasure group was included to identify whether exercise during bed rest might counteract any vasoconstrictor deficits that arose during HDBR. Twenty-two subjects underwent 14 days of strict 6 degrees HDBR. Eight of these 22 subjects did not exercise during HDBR, while 14 of these subjects exercised on a supine cycle ergometer for 90 min a day at 75% of pre-bed rest heart rate maximum. To assess alpha-adrenergic vasoconstrictor responsiveness, intradermal microdialysis was used to locally administer norepinephrine (NE), while forearm skin blood flow (SkBF; laser-Doppler flowmetry) was monitored over microdialysis membranes. Nonlinear regression modeling was used to identify the effective drug concentration that caused 50% of the cutaneous vasoconstrictor response (EC(50)) and minimum values from the SkBF-NE dose-response curves. In addition, the effects of HDBR on nonadrenergic cutaneous vasoconstriction were assessed via the venoarteriolar response of the forearm and leg. HDBR did not alter EC(50) or the magnitude of cutaneous vasoconstriction to exogenous NE administration regardless of whether the subjects exercised during HDBR. Moreover, HDBR did not alter the forearm venoarteriolar response in either the control or exercise groups during HDBR. However, HDBR significantly reduced the magnitude of cutaneous vasoconstriction due to the venoarteriolar response in the leg, and this response was similarly reduced in the exercise group. These data suggest that HDBR does not alter cutaneous vasoconstrictor responses to exogenous NE administration, whereas cutaneous vasoconstriction of the leg due to the venoarteriolar response is reduced after HDBR. It remains unclear whether attenuated venoarteriolar responses in the lower limbs contribute to reduced orthostatic tolerance after bed rest and spaceflight.