Hoeldtke R D, Cilmi K M
J Clin Endocrinol Metab. 1985 Mar;60(3):479-84. doi: 10.1210/jcem-60-3-479.
To determine the cause of the high plasma norepinephrine (NE) concentrations in elderly subjects, we measured apparent NE secretion, NE plasma clearance, and NE production in 14 young and 13 elderly normal subjects. Apparent NE secretion, estimated by isotope dilution analysis, was higher (P less than 0.01) in the elderly subjects [3.08 +/- 0.45 (+/- SEM) nmol/m2 X min] than in the young subjects (1.84 +/- 0.12 nmol/m2 X min). Plasma clearance of NE did not differ between the young (1470 +/- 120 ml/m2 X min) and the elderly (1295 +/- 153) subjects. NE production, estimated from NE metabolite excretion, was 9.66 +/- 0.8 nmol/m2 X min in the elderly subjects, not significantly different from that in the young subjects, who produced NE at a rate of 11.7 +/- 1.1 nmol/m2 X min. Excretion of the O-methyl derivative of NE normetanephrine was increased (P less than 0.01) in the aged, whereas excretion of the deaminated metabolites vanillylmandelic acid and dihydroxmandelic acid was decreased. Our data indicate that the rate at which NE enters the circulation is increased in the elderly, but NE production is normal. Taken together, these results suggest that in aging, there is an alteration in the local disposition of sympathetic neuronal NE.
为确定老年受试者血浆去甲肾上腺素（NE）浓度升高的原因，我们测定了14名年轻和13名老年正常受试者的表观NE分泌、NE血浆清除率及NE生成量。通过同位素稀释分析估算的表观NE分泌，老年受试者[3.08±0.45（±标准误）nmol/m²·min]高于年轻受试者（1.84±0.12 nmol/m²·min）（P<0.01）。年轻受试者（1470±120 ml/m²·min）和老年受试者（1295±153）的NE血浆清除率无差异。根据NE代谢产物排泄估算的NE生成量，老年受试者为9.66±0.8 nmol/m²·min，与年轻受试者[生成速率为11.7±1.1 nmol/m²·min]无显著差异。老年受试者中去甲肾上腺素的O-甲基衍生物去甲变肾上腺素的排泄增加（P<0.01），而脱氨基代谢产物香草扁桃酸和二羟扁桃酸的排泄减少。我们的数据表明，老年受试者中NE进入循环的速率增加，但NE生成正常。综上所述，这些结果提示，在衰老过程中，交感神经元NE的局部处置发生了改变。
