Document Detail

Effect of hindlimb unloading on salt and water intake and output in male and female rats.
MedLine Citation:
PMID:  18580404     Owner:  NLM     Status:  In-Process    
INTRODUCTION/PURPOSE: Although fluid intake decreases during spaceflight, there is no increase in urine output, despite the microgravity-induced cephalic fluid shifts. We proposed that fluid and electrolyte balance is controlled not only by cardiac receptors but also by splanchnic baroreceptors. METHODS: Male and female rats bearing indwelling intravenous cannulae, were subjected to hindlimb unloading (HU) for 24 h at 30 degrees . Water and salt (3% saline) intake, urine output, and plasma osmolality were measured. Right atrial pressure (RAP) and splenic blood pressure/flow were measured during tilt. RESULTS: Whereas HU reduced water intake in both males (100.9 +/- 9.0 to 71.8 +/- 6.1 and females (118.9 +/- 8.9 to 83.1 +/- 6.5 mL x kg), there was a sustained increase in urine volume only in females (males: 30.9 +/- 3.8 to 34.0 +/- 2.8; females: 26.3 +/- 3.8 to 41.1 +/- 5.8 HU did not change sodium intake/output in either males or females. Plasma osmolality (321.8 +/- 24.1 to 347.5 +/- 22.7 mOsm x L) increased in females but not in males (349.2 +/- 3.3 to 354.4 +/- 7.7 mOsm x L). HU was associated not only with increased RAP but also with reduced splenic perfusion: splenic venous pressure/flow decreased by 0.90 +/- 0.16 mm Hg and 0.19 +/- 0.01 mL.min, respectively; splenic arterial pressure/flow decreased by 3.97 +/- 1.68 mm Hg and 0.17 +/- 0.06 mL x min, respectively. CONCLUSION: We propose that it is the balance between discordant signals from cardiac and splenic baroreceptors that controls ingestion and excretion. The ultimate reflex response thus depends on the differential effects of changes in gravity on systemic hemodynamics.
Heather Edgell; Susan Kaufman
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Medicine and science in sports and exercise     Volume:  40     ISSN:  0195-9131     ISO Abbreviation:  Med Sci Sports Exerc     Publication Date:  2008 Jul 
Date Detail:
Created Date:  2008-06-26     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8005433     Medline TA:  Med Sci Sports Exerc     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1249-54     Citation Subset:  IM; S    
Department of Physiology, University of Alberta, Edmonton, Alberta, CANADA.
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