Greenleaf J E, Petersen T W, Gabrielsen A, Pump B, Bie P, Christensen N J, Warberg J, Videbaek R, Simonson S R, Norsk P
Danish Aerospace Medical Centre of Research and Clinic of Aviation Medicine, Rigshospitalet; DK-2200 Copenhagen, Denmark.
Am J Physiol Regul Integr Comp Physiol. 2000 Sep;279(3):R822-9. doi: 10.1152/ajpregu.2000.279.3.R822.
Plasma vasoactive hormone concentrations [epinephrine (p(Epi)), norepinephrine (p(NE)), ANG II (p(ANG II)), vasopressin (p(VP)), endothelin-1 (p(ET-1))] and plasma renin activity (p(RA)) were measured periodically and compared during lower body negative pressure (LBNP) to test the hypothesis that responsiveness of the renin-angiotensin system, the latter being one of the most powerful vasoconstrictors in the body, is of major importance for LBNP tolerance. Healthy men on a controlled diet (2,822 cal/day, 2 mmol. kg(-1). day(-1) Na(+)) were exposed to 30 min of LBNP from -15 to -50 mmHg. LBNP was uneventful for seven men [25 +/- 2 yr, high-tolerance (HiTol) group], but eight men (26 +/- 3 yr) reached presyncope after 11 +/- 1 min [P < 0.001, low-tolerance (LoTol) group]. Mean arterial pressure (MAP) did not change measurably, but central venous pressure and left atrial diameter decreased similarly in both groups (5-6 mmHg, by approximately 30%, P < 0.05). Control (0 mmHg LBNP) hormone concentrations were similar between groups, however, p(RA) differed between them (LoTol 0.6 +/- 0.1, HiTol 1.2 +/- 0.1 ng ANG I. ml(-1). h(-1), P < 0.05). LBNP increased (P < 0. 05) p(RA) and p(ANG II), respectively, more in the HiTol group (9.9 +/- 2.2 ng ANG I. ml(-1). h(-1) and 58 +/- 12 pg/ml) than in LoTol subjects (4.3 +/- 0.9 ng ANG I. ml(-1). h(-1) and 28 +/- 6 pg/ml). In contrast, the increase in p(VP) was higher (P < 0.05) in the LoTol than in the HiTol group. The increases (P < 0.05) for p(NE) were nonsignificant between groups, and p(ET-1) remained unchanged. Thus there may be a causal relationship between attenuated activation of p(RA) and p(ANG II) and presyncope, with p(VP) being a possible cofactor. Measurement of resting p(RA) may be of predictive value for those with lower hypotensive tolerance.
定期测量血浆血管活性激素浓度[肾上腺素(p(Epi))、去甲肾上腺素(p(NE))、血管紧张素II(p(ANG II))、血管加压素(p(VP))、内皮素-1(p(ET-1))]和血浆肾素活性(p(RA))，并在下肢负压(LBNP)期间进行比较，以检验肾素-血管紧张素系统（后者是体内最强大的血管收缩剂之一）的反应性对LBNP耐受性至关重要这一假设。让食用控制饮食（2822千卡/天，2毫摩尔·千克⁻¹·天⁻¹钠）的健康男性暴露于-15至-50 mmHg的LBNP 30分钟。LBNP对7名男性[25±2岁，高耐受性(HiTol)组]来说进展顺利，但8名男性(26±3岁)在11±1分钟后出现了接近晕厥的症状[P<0.001，低耐受性(LoTol)组]。平均动脉压(MAP)没有明显变化，但两组的中心静脉压和左心房直径均有类似程度的下降(5-6 mmHg，约30%，P<0.05)。两组之间对照(0 mmHg LBNP)时的激素浓度相似，然而，它们之间的p(RA)有所不同(LoTol组为0.6±0.1，HiTol组为1.2±0.1 ng血管紧张素I·毫升⁻¹·小时⁻¹，P<0.05)。LBNP使HiTol组的p(RA)和p(ANG II)分别升高得更多(P<0.05)(分别为9.9±2.2 ng血管紧张素I·毫升⁻¹·小时⁻¹和58±12 pg/ml)，高于LoTol组受试者(4.3±0.9 ng血管紧张素I·毫升⁻¹·小时⁻¹和28±6 pg/ml)。相比之下，LoTol组p(VP)的升高高于HiTol组(P<0.05)。两组之间p(NE)的升高(P<0.05)无显著差异，p(ET-1)保持不变。因此，p(RA)和p(ANG II)激活减弱与接近晕厥之间可能存在因果关系，p(VP)可能是一个辅助因素。静息p(RA)的测量对于低血压耐受性较低的人可能具有预测价值。
