Document Detail

Changes in the renal handling of urea in sheep on a low protein diet exposed to saline drinking water.
MedLine Citation:
PMID:  15580763     Owner:  NLM     Status:  MEDLINE    
Previous trials have demonstrated that sheep on a low protein diet and free access to water, and sheep dosed with boluses of NaCl intraruminally also with free access to water, showed decreases in urea loss via the urine compared to control animals. We monitored urea excretion in sheep on a relatively poor protein diet when they were exposed to saline drinking water, i.e. they were unable to vary their intake of NaCl:water. Sheep on isotonic saline drinking water (phase 3) excreted significantly more urea via the urine (284 mM/day) compared to phase 1 when they were on non-saline drinking water (urea excretion = 230 mM/day) and phase 2 when they were on half isotonic saline drinking water (urea excretion = 244 mM/day). This finding was explained by the high glomerular filtration rate (GFR) 91.9 l/day, compared to 82.4 l/day (phase 1) and 77.9 l/day (phase 2), together with a significantly raised fractional excretion of urea (FEurea) (51.1 %) during this phase, and was in spite of the significantly lower plasma concentrations of urea in phase 3 compared to phase 1. The FEurea probably results from the osmotic diuresis caused by the salt. There were indications of a raised plasma antidiuretic hormone (ADH) concentration and this would have opposed urea loss, as ADH promotes urea reabsorption. However, this ADH effect was probably counteracted to some extent by a low plasma angiotensin II concentration, for which again there were indications, inhibiting urea reabsorption during the phases of salt loading. As atrial natriuretic peptide both increases GFR and decrease sodium reabsorption from the tubule, it was probably instrumental in causing the increase in GFR and the increase in the fractional excretion of sodium (FE(Na)).
R A Meintjes; H Engelbrecht
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Onderstepoort journal of veterinary research     Volume:  71     ISSN:  0030-2465     ISO Abbreviation:  Onderstepoort J. Vet. Res.     Publication Date:  2004 Sep 
Date Detail:
Created Date:  2004-12-07     Completed Date:  2005-04-18     Revised Date:  2009-11-03    
Medline Journal Info:
Nlm Unique ID:  0401107     Medline TA:  Onderstepoort J Vet Res     Country:  South Africa    
Other Details:
Languages:  eng     Pagination:  165-70     Citation Subset:  IM    
Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110 South Africa.
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MeSH Terms
Dietary Proteins / administration & dosage*
Glomerular Filtration Rate / veterinary
Kidney / metabolism*
Sheep / metabolism*
Sodium Chloride / pharmacology*
Urea / metabolism,  urine*
Vasopressins / blood
Reg. No./Substance:
0/Dietary Proteins; 11000-17-2/Vasopressins; 57-13-6/Urea; 7647-14-5/Sodium Chloride

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