Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA.
J Appl Physiol (1985). 2013 Aug 15;115(4):446-55. doi: 10.1152/japplphysiol.00446.2013. Epub 2013 Jun 20.
We tested the hypothesis that reduced nitric oxide (NO) bioavailability contributes to the attenuated peak and total vasodilation following single-muscle contractions in older adults. Young (n = 10; 24 ± 2 yr) and older (n = 10; 67 ± 2 yr) adults performed single forearm contractions at 10, 20, and 40% of maximum during saline infusion (control) and NO synthase (NOS) inhibition via N(G)-monomethyl-l-arginine. Brachial artery diameters and velocities were measured using Doppler ultrasound and forearm vascular conductance (FVC; in ml·min(-1)·100 mmHg(-1)) was calculated from blood flow (ml/min) and blood pressure (mmHg). Peak and total vasodilator responses [change (Δ) in FVC from baseline] were attenuated in older adults at all intensities (P < 0.05). NOS inhibition reduced the peak ΔFVC at 10% (88 ± 12 vs. 52 ± 9 ml·min(-1)·100 mmHg(-1)), 20% (125 ± 13 vs. 83 ± 13 ml·min(-1)·100 mmHg(-1)), and 40% (207 ± 26 vs. 133 ± 20 ml·min(-1)·100 mmHg(-1)) in young subjects, (P < 0.05 for all) and in older adults at 10% (59 ± 5 vs. 47 ± 7 ml·min(-1)·100 mmHg(-1), P < 0.05) and 20% (88 ± 9 vs. 68 ± 9 ml·min(-1)·100 mmHg(-1), P < 0.05), but not 40% (128 ± 12 vs. 105 ± 11 ml·min(-1)·100 mmHg(-1), P = 0.11). The relative (%) reduction in peak ΔFVC due to NOS inhibition was greater in young vs. older adults at 20% (-36 ± 5 vs. -23 ± 5%, P < 0.05) and 40% (-35 ± 6 vs. -16 ± 7%, P < 0.05). The reduction in the total vasodilator response (area under the curve) with NOS inhibition was also greater in young vs. older adults at all intensities. Our data suggest that contraction-induced rapid vasodilation is mediated in part by NO, and that the contribution of NO is greater in young adults.
我们检验了这样一个假设，即减少的一氧化氮（NO）生物利用度导致老年人单次肌肉收缩后的峰值和总血管扩张减弱。年轻组（n=10；24±2 岁）和老年组（n=10；67±2 岁）在生理盐水输注期间（对照）和通过 N(G)-单甲基-L-精氨酸抑制一氧化氮合酶（NOS）时，以 10%、20%和 40%的最大程度进行单次前臂收缩。肱动脉直径和速度使用多普勒超声测量，前臂血管传导（FVC；ml·min(-1)·100 mmHg(-1)）由血流（ml/min）和血压（mmHg）计算得出。在所有强度下，老年人的峰值和总血管扩张反应[FVC 从基线的变化（Δ）]均减弱（P<0.05）。NOS 抑制降低了年轻人在 10%（88±12 对 52±9 ml·min(-1)·100 mmHg(-1)）、20%（125±13 对 83±13 ml·min(-1)·100 mmHg(-1)）和 40%（207±26 对 133±20 ml·min(-1)·100 mmHg(-1)）时的峰值ΔFVC（所有 P<0.05），以及在老年人的 10%（59±5 对 47±7 ml·min(-1)·100 mmHg(-1)，P<0.05）和 20%（88±9 对 68±9 ml·min(-1)·100 mmHg(-1)，P<0.05）时的峰值ΔFVC（所有 P<0.05），但在 40%时没有（128±12 对 105±11 ml·min(-1)·100 mmHg(-1)，P=0.11）。由于 NOS 抑制，年轻人的峰值ΔFVC 相对（%）减少幅度大于老年人，在 20%（-36±5 对-23±5%，P<0.05）和 40%（-35±6 对-16±7%，P<0.05）时更大。在所有强度下，NOS 抑制引起的总血管扩张反应（曲线下面积）减少幅度也大于年轻人。我们的数据表明，收缩引起的快速血管扩张部分是由 NO 介导的，并且在年轻人中 NO 的贡献更大。
