Hausdorff J M, Clark B A, Shannon R P, Elahi D, Wei J Y
Charles A. Dana Research Institute, Boston, USA.
J Gerontol A Biol Sci Med Sci. 1995 May;50(3):M169-72. doi: 10.1093/gerona/50a.3.m169.
Plasma levels of atrial natriuretic peptide (ANP) increase with age. To test the hypothesis that the cardiovascular response to ANP is age dependent and to examine the role of the increased levels of ANP in the hypotensive response to orthostatic challenge, we compared the hemodynamic response of young and elderly subjects to ANP infusion and orthostatic challenge.
Blood pressure, heart rate, forearm cutaneous resistance, plasma ANP, and plasma norepinephrine were measured in the supine position and following upright tilt before and after a 60-minute infusion of atrial natriuretic peptide (0.05 microgram/kg/min) in 7 young (27 +/- 4 years) and 5 elderly (74 +/- 4 years) normotensive, healthy subjects.
Prior to ANP infusion, the response to upright tilt was similar in both groups. Infusion of ANP produced similar steady state plasma levels of ANP in both groups (young: 435 +/- 49 pg/ml; elderly: 429 +/- 32 pg/ml). Supine systolic blood pressure decreased by 4 +/- 2 mmHg in the young subjects and by 18 +/- 8 mmHg in the elderly subjects after infusion (p < .08). In contrast, changes in supine heart rate, forearm cutaneous resistance, and plasma norepinephrine were similar in both groups (delta heart rate: young +5 +/- 3 beats/min, elderly +4 +/- 2 beats/min; delta forearm cutaneous resistance: young -38 +/- 9%, elderly -40 +/- 6%; delta norepinephrine: young +55 +/- 11%, elderly: +43 +/- 13%). ANP infusion abolished the vasoconstrictor response normally associated with orthostatic challenge in both groups, despite a significant release of catecholemines and an enhanced heart rate response. This resulted in significant systolic blood pressure reduction in both young (-7 +/- 2 mmHg, p < .05) and elderly subjects (-16 +/- 4 mmHg, p < .05). The drop in systolic blood pressure in response to upright tilt and ANP infusion was four times larger in the elderly subjects (change from pre-ANP level: young -8 +/- 3 mmHg, elderly -32 +/- 5 mmHg, p < .005).
心房利钠肽（ANP）的血浆水平随年龄增长而升高。为了验证心血管系统对ANP的反应是否依赖于年龄这一假设，并探究ANP水平升高在体位性低血压反应中的作用，我们比较了年轻和老年受试者对ANP输注及体位性低血压刺激的血流动力学反应。
在7名年轻（27±4岁）和5名老年（74±4岁）血压正常的健康受试者中，测量了仰卧位以及直立倾斜后静息状态下、输注心房利钠肽（0.05微克/千克/分钟）60分钟前和后的血压、心率、前臂皮肤电阻、血浆ANP和血浆去甲肾上腺素水平。
在输注ANP之前，两组对直立倾斜的反应相似。输注ANP后，两组的ANP血浆稳态水平相似（年轻组：435±49皮克/毫升；老年组：429±32皮克/毫升）。输注后，年轻受试者仰卧位收缩压下降4±2毫米汞柱，老年受试者下降18±8毫米汞柱（p<0.08）。相比之下，两组仰卧位心率、前臂皮肤电阻和血浆去甲肾上腺素的变化相似（心率变化：年轻组+5±3次/分钟，老年组+4±2次/分钟；前臂皮肤电阻变化：年轻组-38±9%，老年组-40±6%；去甲肾上腺素变化：年轻组+55±11%，老年组+43±13%）。尽管儿茶酚胺大量释放且心率反应增强，但输注ANP消除了两组通常与体位性低血压刺激相关的血管收缩反应。这导致年轻受试者（-7±2毫米汞柱，p<0.05）和老年受试者（-16±4毫米汞柱，p<0.05）的收缩压显著降低。老年受试者因直立倾斜和ANP输注导致的收缩压下降幅度是年轻受试者的四倍（相对于输注ANP前水平的变化：年轻组-8±3毫米汞柱，老年组-32±5毫米汞柱，p<0.005）。
