Renal and neurohormonal responses to increasing levels of lower body negative pressure in men
| Autor: | Arnaud Chiolero, Michel Burnier, Jürg Nussberger, Marc Maillard, Grégoire Würzner, Hans R. Brunner, Daniel Hayoz |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
Adult
Male medicine.medical_specialty Sympathetic nervous system Renal function Hemodynamics Nephron Kidney Renal Circulation chemistry.chemical_compound Internal medicine Medicine Humans sympathetic nervous system Lower Body Negative Pressure Neurotransmitter Agents Aldosterone aldosterone Cross-Over Studies Renal sodium reabsorption business.industry Reabsorption orthostatic stress Sodium blood pressure sodium handling medicine.anatomical_structure Endocrinology Kidney Tubules chemistry renin Nephrology business renal sympathetic nerve |
| Zdroj: | Kidney International. 60(4):1469-1476 |
| ISSN: | 0085-2538 |
| DOI: | 10.1046/j.1523-1755.2001.00950.x |
| Popis: | Renal and neurohormonal responses to increasing levels of lower body negative pressure in men.BackgroundThe stimulation of efferent renal sympathetic nerve activity induces sequential changes in renin secretion, sodium excretion, and renal hemodynamics that are proportional to the magnitude of the stimulation of sympathetic nerves. This study in men investigated the sequence of the changes in proximal and distal renal sodium handling, renal and systemic hemodynamics, as well as the hormonal profile occurring during a sustained activation of the sympathetic nervous system induced by various levels of lower body negative pressure (LBNP).MethodsTen healthy subjects were submitted to three levels of LBNP ranging between 0 and -22.5mm Hg for one hour according to a triple crossover design, with a minimum of five days between each level of LBNP. Systemic and renal hemodynamics, renal water and sodium handling (using the endogenous lithium clearance technique), and the neurohormonal profile were measured before, during, and after LBNP.ResultsLBNP (0 to -22.5mm Hg) induced an important hormonal response characterized by a significant stimulation of the sympathetic nervous system and gradual activations of the vasopressin and the renin-angiotensin systems. LBNP also gradually reduced water excretion and increased urinary osmolality. A significant decrease in sodium excretion was apparent only at -22.5mm Hg. It was independent of any change in the glomerular filtration rate and was mediated essentially by an increased sodium reabsorption in the proximal tubule (a significant decrease in lithium clearance, P < 0.05). No significant change in renal hemodynamics was found at the tested levels of LBNP. As observed experimentally, there appeared to be a clear sequence of responses to LBNP, the neurohormonal response occurring before the changes in water and sodium excretion, these latter preceding any change in renal hemodynamics.ConclusionsThese data show that the renal sodium retention developing during LBNP, and thus sympathetic nervous stimulation, is due mainly to an increase in sodium reabsorption by the proximal segments of the nephron. Our results in humans also confirm that, depending on its magnitude, LBNP leads to a step-by-step activation of neurohormonal, renal tubular, and renal hemodynamic responses. |
| Databáze: | OpenAIRE |
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