Endocrine responses to 7 days of head‐down bed rest and orthostatic tests in men and women
- 1 March 2001
- journal article
- Published by Wiley in Clinical Physiology and Functional Imaging
- Vol. 21 (2), 172-183
- https://doi.org/10.1046/j.1365-2281.2001.00315.x
Abstract
The objective of this study was to investigate plasma volume (PV), total body water, hormones and hydroelectrolyte responses in eight males (25-40 years) and eight females (25-31 years) during 7 days of exposure to simulated microgravity (-6 degrees head-down bed rest, HDBR). Bed rest is a model that has commonly been used to simulate spaceflight. Heart rate (HR), blood pressure (BP) and vasoactive hormone responses were studied before and after HDBR during a 10-min stand test. No change in total body water and body mass was noted in either sex. The decrease in PV was similar in both men (9.1 +/- 1.4%) and women (9.4 +/- 0.8%). Urinary normetanephrine (NMN) was decreased during HDBR in both sexes. Urinary metanephrine (MN) and plasma catecholamines were unchanged. Daily urinary excretion of urea, an indirect index of protein breakdown, was increased only in the female subjects during HDBR. Plasma active renin (AR) and aldosterone were increased in both sexes, but urinary atrial natriuretic peptide (ANP) and arginine vasopressin (AVP) were unchanged throughout the study. Also, the hormonal responses to 7 days of HDBR were comparable between men and women. Moreover, the results show similar cardiovascular and endocrine responses to standing after HDBR. However, the orthostatic intolerance following HDBR was associated with a blunted increase in noradrenaline (NA) only in the women during the stand test. It is concluded that: (i) 7 days of physical inactivity achieved during HDBR resulted in a reduced sympathetic activity in both sexes and alterations in protein metabolism in women and (ii) standing after HDBR resulted in an attenuated release of noradrenaline in women.Keywords
This publication has 40 references indexed in Scilit:
- Vasoactive neuroendocrine responses associated with tolerance to lower body negative pressure in humansClinical Physiology and Functional Imaging, 2000
- Energy and Water Metabolism, Body Composition, and Hormonal Changes Induced by 42 Days of Enforced Inactivity and Simulated WeightlessnessJournal of Clinical Endocrinology & Metabolism, 1998
- EFFECT OF GENDER ON ORTHOSTATIC TOLERANCE.Medicine & Science in Sports & Exercise, 1995
- Blood volume regulating hormones response during two space related simulation protocols: Four-week confinement and head-down bed-restActa Astronautica, 1995
- Blood Volume Responses of Men and Women to Bed RestThe Journal of Clinical Pharmacology, 1994
- Repeated plasma volume determination with the Evans Blue dye dilution technique: The method and a computer programComputers in Biology and Medicine, 1991
- Plasma free and sulphated catecholamines after ultra-long exercise and recoveryEuropean Journal of Applied Physiology, 1990
- Analysis of nitrate, nitrite, and [15N]nitrate in biological fluidsAnalytical Biochemistry, 1982
- Cardiorespiratory responses to exercise after bed rest in men and womenActa Astronautica, 1977
- Bemerkungen zu der Abhandlung der HH. Weselsky und Benedikt „Ueber einige Azoverbindungen”︁European Journal of Inorganic Chemistry, 1879