Ford G A, Dachman W D, Blaschke T F, Hoffman B B
Department of Medicine, Stanford University School of Medicine 94305.
J Appl Physiol (1985). 1995 Jan;78(1):172-8. doi: 10.1152/jappl.1995.78.1.172.
beta-Adrenergic responses have been shown to decline with aging, particularly in the cardiovascular system. We infused terbutaline, a selective beta 2-adrenoceptor agonist, into the brachial artery of 10 young (mean age 25 yr, range 22-31 yr) and 9 elderly (mean age 73 yr, range 68-81 yr) healthy subjects to examine its effects on nutrient flux. Forearm K+, PO4, free fatty acid (FFA), and glycerol uptake were determined by measurement of forearm blood flow (using dye dilution) and brachial arterial and deep venous plasma substrate concentrations. Elderly subjects were less sensitive to terbutaline-mediated increases in forearm blood flow, net fluxes of K+, and glycerol but not net fluxes of FFA or PO4. The mean fitted slopes of each parameter vs. the log of the terbutaline concentration, a measure of forearm beta-adrenergic sensitivity, for young and elderly groups were 4.9 +/- 1.7 (SD) vs. 2.4 +/- 2.3 for forearm blood flow (P < 0.05), 0.84 +/- 0.46 vs. 0.43 +/- 0.37 for K+ net flux (P < 0.05), -157 +/- 113 vs. -26 +/- 26 for glycerol net flux (P < 0.01), -336 +/- 429 vs. -44 +/- 457 for FFA net flux (P = 0.11), and 0.31 +/- 0.24 vs. 0.18 +/- 0.16 for PO4 net flux (P = 0.14). Terbutaline promoted net uptake of K+ into skeletal muscle less well in the elderly, although net PO4 flux was similar in the two groups. Terbutaline-stimulated vasodilation and net glycerol efflux but not FFA efflux were impaired with aging. These data demonstrate that heterogeneous changes in beta-adrenergic responses occur with aging.
β-肾上腺素能反应已被证明会随着年龄增长而下降，尤其是在心血管系统中。我们将选择性β2-肾上腺素能受体激动剂特布他林注入10名年轻（平均年龄25岁，范围22 - 31岁）和9名老年（平均年龄73岁，范围68 - 81岁）健康受试者的肱动脉，以检查其对营养物质通量的影响。通过测量前臂血流量（使用染料稀释法）以及肱动脉和深静脉血浆底物浓度来测定前臂钾离子（K+）、磷酸根（PO4）、游离脂肪酸（FFA）和甘油摄取量。老年受试者对特布他林介导的前臂血流量增加、K+和甘油的净通量反应较不敏感，但对FFA或PO4的净通量反应并非如此。年轻组和老年组各参数相对于特布他林浓度对数的平均拟合斜率（衡量前臂β-肾上腺素能敏感性），对于前臂血流量分别为4.9±1.7（标准差）和2.4±2.3（P<0.05），对于K+净通量分别为0.84±0.46和0.43±0.37（P<0.05），对于甘油净通量分别为 - 157±113和 - 26±26（P<0.01），对于FFA净通量分别为 - 336±429和 - 44±457（P = 0.11），对于PO4净通量分别为0.31±0.24和0.18±0.16（P = 0.14）。特布他林促进K+净摄取进入老年骨骼肌的效果较差，尽管两组的PO4净通量相似。随着年龄增长，特布他林刺激的血管舒张和甘油净流出受损，但FFA流出未受影响。这些数据表明，β-肾上腺素能反应会随着年龄增长发生异质性变化。
