Hogikyan R V, Supiano M A
Department of Internal Medicine, University of Michigan, Ann Arbor.
Am J Physiol. 1994 May;266(5 Pt 1):E717-24. doi: 10.1152/ajpendo.1994.266.5.E717.
We tested the hypotheses that 1) there is an age-associated decrease in arterial alpha-adrenergic responsiveness and 2) there is upregulation of this response during suppression of sympathetic nervous system (SNS) activity. We measured forearm blood flow (FABF) by plethysmography during brachial artery infusions of the alpha-adrenergic agonist norepinephrine (NE) and the nonadrenergic agonist angiotensin II (ANG II) in 15 young and 14 older healthy human subjects. Among the old (O) relative to the young (Y) we identified greater plasma NE levels (Y: 1.29 +/- 0.07 nM vs. O: 2.14 +/- 0.17 nM; P = 0.0001); a decrease in NE-mediated reduction in FABF [analysis of variance (ANOVA) P = 0.04]; and, in contrast, no difference in ANG II-mediated reduction in FABF (ANOVA P = 0.43). In the nine older subjects studied during guanadrel (G) to suppress SNS activity, we identified decreased plasma NE levels [placebo (P): 2.11 +/- 0.24 nM vs. G: 1.09 +/- 0.09 nM; P = 0.002], increased NE-mediated FABF response (ANOVA P = 0.01), and no difference in FABF response to ANG II (ANOVA: P = 0.69) compared with P. We conclude that there is appropriate desensitization of arterial alpha-adrenergic responsiveness among the older relative to the young subjects that is specific for the alpha-adrenergic system. Among the older subjects there is homologous upregulation of this response when SNS activity is suppressed.
1）动脉α-肾上腺素能反应性存在与年龄相关的下降；2）在交感神经系统（SNS）活动受抑制期间，这种反应会上调。我们通过体积描记法测量了15名年轻和14名老年健康受试者在肱动脉输注α-肾上腺素能激动剂去甲肾上腺素（NE）和非肾上腺素能激动剂血管紧张素II（ANG II）期间的前臂血流量（FABF）。与年轻受试者（Y）相比，老年受试者（O）的血浆NE水平更高（Y：1.29±0.07 nM vs. O：2.14±0.17 nM；P = 0.0001）；NE介导的FABF降低有所减少[方差分析（ANOVA）P = 0.04]；相反，ANG II介导的FABF降低无差异（ANOVA P = 0.43）。在9名接受胍那决尔（G）治疗以抑制SNS活动的老年受试者中，与安慰剂（P）相比，我们发现血浆NE水平降低[P：2.11±0.24 nM vs. G：1.09±0.09 nM；P = 0.002]，NE介导的FABF反应增加（ANOVA P = 0.01），且FABF对ANG II的反应无差异（ANOVA：P = 0.69）。我们得出结论，相对于年轻受试者，老年受试者的动脉α-肾上腺素能反应性存在适当的脱敏，这对α-肾上腺素能系统具有特异性。在老年受试者中，当SNS活动受抑制时，这种反应会发生同源性上调。
