School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Birmingham, United Kingdom.
NeuroV̇ASQ̇ - Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Distrito Federal, Brazil.
J Appl Physiol (1985). 2020 Dec 1;129(6):1373-1382. doi: 10.1152/japplphysiol.00296.2020. Epub 2020 Oct 8.
We sought to determine how whole body heating acutely influences radial artery function, characterized using flow-mediated dilation (FMD) and low-flow-mediated constriction (L-FMC), and the mechanistic role of shear rate modification on radial artery functional characteristics during heating. Eleven young healthy men underwent whole body heating (water-perfused suit) sufficient to raise the core temperature by +1°C. Trials were repeated with (heat + WC) and without (heat) the application of a wrist cuff located distal to the radial artery examined, known to prevent increases in mean and anterograde shear rates but increase retrograde shear rate. Radial artery characteristics were assessed throughout each trial, with FMD and L-FMC assessed before and upon reaching the target core temperature. Heat markedly increased radial artery mean and anterograde shear rates, along with radial artery diameter and blood flow ( < 0.05). Heat + WC abolished the heat-induced increase in mean and anterograde shear rates ( > 0.05) but markedly increased retrograde shear rate ( < 0.05). Concomitantly, increases in radial artery diameter and blood flow were decreased (heat + WC vs. heat, < 0.05). Heat attenuated FMD (8.6 ± 1.2% vs. 2.2 ± 1.4%, < 0.05), whereas no change in FMD was observed in heat + WC (7.8 ± 1.2% vs. 10.8 ± 1.2%, > 0.05). In contrast, L-FMC was not different in either trial ( > 0.05). In summary, acute whole body heating markedly elevates radial artery shear rate, diameter, and blood flow and diminishes FMD. However, marked radial artery vasodilation and diminished FMD are absent when these shear rate changes are prevented. Shear rate modifications underpin the radial artery response to acute whole body heat stress, but further endothelium-dependent vasodilation (FMD) is attenuated likely as the vasodilatory range limit is approached. We observed that acute whole body heating elevates radial artery shear rate, diameter, and blood flow. This results in a diminished flow-meditated dilatation (FMD) but does not change low-flow-mediated constriction (L-FMC). Preventing shear rate changes during whole body heating reduces radial artery vasodilation and reverses FMD reductions but has no effect on L-FMC. These findings indicate that shear rate changes underpin conduit artery responses to acute whole body heat stress, but further endothelium-dependent flow-mediated vasodilation is attenuated as the vasodilatory range limit is approached.
我们旨在确定全身加热如何急性影响桡动脉功能，其特征在于使用血流介导的扩张（FMD）和低血流介导的收缩（L-FMC），以及在加热过程中剪切率改变对桡动脉功能特征的机械作用。11 名年轻健康男性接受全身加热（水灌注服），足以将核心温度升高+1°C。在应用位于桡动脉检查部位远端的腕带（已知可防止平均和前向剪切率增加，但增加后向剪切率）（热+WC）和不应用腕带（热）的情况下重复试验。在每次试验中评估桡动脉特征，在达到目标核心温度之前和之后评估 FMD 和 L-FMC。热显着增加桡动脉平均和前向剪切率，以及桡动脉直径和血流（<0.05）。热+WC 消除了热引起的平均和前向剪切率的增加（>0.05），但显着增加了后向剪切率（<0.05）。同时，桡动脉直径和血流的增加减少（热+WC 与热，<0.05）。热显着减弱 FMD（8.6±1.2%比 2.2±1.4%，<0.05），而热+WC 中 FMD 没有变化（7.8±1.2%比 10.8±1.2%，>0.05）。相比之下，在任何试验中 L-FMC 均无差异（>0.05）。总之，全身急性加热显着增加桡动脉剪切率、直径和血流，并减弱 FMD。然而，当这些剪切率变化得到预防时，明显的桡动脉血管舒张和 FMD 减弱则不存在。剪切率的改变为急性全身热应激时桡动脉的反应提供了基础，但由于接近血管舒张范围的限制，进一步的内皮依赖性血管舒张（FMD）减弱。我们观察到全身急性加热会增加桡动脉的剪切率、直径和血流。这导致血流介导的扩张（FMD）减弱，但不会改变低血流介导的收缩（L-FMC）。在全身加热期间防止剪切率变化会减少桡动脉血管舒张并逆转 FMD 降低，但对 L-FMC 没有影响。这些发现表明，剪切率的变化为急性全身热应激时的主要动脉反应提供了基础，但随着血管舒张范围的限制接近，进一步的内皮依赖性血流介导的血管舒张减弱。
