Clark Christine M, Monahan Kevin D, Drew Rachel C
Pennsylvania State University College of Medicine, Hershey, Pennsylvania; and.
Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania.
Am J Physiol Regul Integr Comp Physiol. 2015 Dec 15;309(12):R1474-8. doi: 10.1152/ajpregu.00291.2015. Epub 2015 Oct 14.
The ability of the human body to maintain arterial blood pressure (BP) during orthostatic stress is determined by several reflex neural mechanisms. Renal vasoconstriction progressively increases during graded elevations in lower body negative pressure (LBNP). This sympathetically mediated response redistributes blood flow to the systemic circulation to maintain BP. However, how healthy aging affects the renal vasoconstrictor response to LBNP is unknown. Therefore, 10 young (25 ± 1 yr; means ± SE) and 10 older (66 ± 2 yr) subjects underwent graded LBNP (-15 and -30 mmHg) while beat-to-beat renal blood flow velocity (RBFV; Doppler ultrasound), arterial BP (Finometer), and heart rate (HR; electrocardiogram) were recorded. Renal vascular resistance (RVR), an index of renal vasoconstriction, was calculated as mean BP/RBFV. All baseline cardiovascular variables were similar between groups, except diastolic BP was higher in older subjects (P < 0.05). Increases in RVR during LBNP were greater in the older group compared with the young group (older: -15 mmHg Δ10 ± 3%, -30 mmHg Δ20 ± 5%; young: -15 mmHg Δ2 ± 2%, -30 mmHg Δ6 ± 2%; P < 0.05). RBFV tended to decrease more (P = 0.10) and mean BP tended to decrease less (P = 0.09) during LBNP in the older group compared with the young group. Systolic and diastolic BP, pulse pressure, and HR responses to LBNP were similar between groups. These findings suggest that aging augments the renal vasoconstrictor response to orthostatic stress in humans.
人体在体位性应激期间维持动脉血压（BP）的能力由多种反射性神经机制决定。在下半身负压（LBNP）分级升高过程中，肾血管收缩会逐渐增强。这种由交感神经介导的反应会将血流重新分配到体循环以维持血压。然而，健康衰老如何影响肾脏对LBNP的血管收缩反应尚不清楚。因此，10名年轻受试者（25±1岁；均值±标准误）和10名老年受试者（66±2岁）接受了分级LBNP（-15和-30 mmHg），同时记录逐搏肾血流速度（RBFV；多普勒超声）、动脉血压（Finometer）和心率（HR；心电图）。肾血管阻力（RVR）作为肾血管收缩的指标，计算方法为平均血压/RBFV。除老年受试者的舒张压较高外（P<0.05），两组之间所有基线心血管变量均相似。与年轻组相比，老年组在LBNP期间RVR的增加幅度更大（老年组：-15 mmHg时增加10±3%，-30 mmHg时增加20±5%；年轻组：-15 mmHg时增加2±2%，-30 mmHg时增加6±2%；P<0.05）。与年轻组相比，老年组在LBNP期间RBFV的下降趋势更明显（P = 0.10），而平均血压的下降趋势则较小（P = 0.09）。两组之间对LBNP的收缩压、舒张压、脉压和心率反应相似。这些发现表明，衰老增强了人体对体位性应激的肾血管收缩反应。
