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| Effect of standing on neurohumoral responses and plasma volume in healthy subjects |
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| Author(s): Jacob G, Ertl AC, Shannon JR, Furlan R, Robertson RM, Robertson D |
| Source: JOURNAL OF APPLIED PHYSIOLOGY Volume: 84 Issue: 3 Pages: 914-921 Published: MAR 1998 |
| Times Cited: 45 References: 33 |
| Abstract: Upright posture leads to rapid pooling of blood in the lower extremities and shifts plasma fluid into surrounding tissues. This results in a decrease in plasma volume (PV) and in hemoconcentration. There has been no integrative evaluation of concomitant neurohumoral and PV shifts with upright posture in normal subjects. We studied 10 healthy subjects after 3 days of stable Na+ and K+ intake. PV was assessed by the Evans blue dye method and by changes in hematocrit. Norepinephrine (NE), NE spillover, epinephrine (Epi), vasopressin, plasma renin activity, aldosterone, osmolarity, and kidney response expressed by urine osmolality and by Na+ and K+ excretion of the subjects in the supine and standing postures were all measured. We found that PV fell by 13% (375 +/- 35 ml plasma) over similar to 14 min, after which time it remained relatively stable. There was a concomitant decrease in systolic blood pressure and an increase in heart rate that peaked at the time of maximal decrease in PV. Plasma Epi and NE increased rapidly to this point. Epi approached baseline by 20 min of standing. NE spillover increased 80% and clearance decreased 30% with 30 min of standing. The increase in plasma renin activity correlated with an increase in aldosterone. Vasopressin increased progressively, but there was no change in plasma osmolarity The kidney response showed a significant decrease in Na+ and an increase in K+ excretion with upright posture. We conclude that a cascade of neurohumoral events occurs with upright posture, some of which particularly coincide with the decrease in PV. Plasma Epi levels mag contribute to the increment in heart rate with maintained upright posture. |
| Document Type: Article |
| Language: English |
| Reprint Address: Robertson, D (reprint author), Vanderbilt Univ, Dept Med, Clin Res Ctr, AA3228 MCN, Nashville, TN 37232 USA |
Addresses:
1. Vanderbilt Univ, Dept Med, Clin Res Ctr, Nashville, TN 37232 USA
2. Vanderbilt Univ, Dept Pharmacol, Nashville, TN 37232 USA
3. Vanderbilt Univ, Dept Neurol, Nashville, TN 37232 USA
4. Rambam Med Ctr, Recanati Auton Dysfunct Ctr, IL-31096 Haifa, Israel |
| Publisher: AMER PHYSIOLOGICAL SOC, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA |
| Subject Category: Physiology; Sport Sciences |
| IDS Number: YZ674 |
| ISSN: 8750-7587 |
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