Document Detail

The alkaline tide goes out and the nitrogen stays in after feeding in the dogfish shark, Squalus acanthias.
MedLine Citation:
PMID:  17656159     Owner:  NLM     Status:  MEDLINE    
In light of previous work showing a marked metabolic alkalosis ("alkaline tide") in the bloodstream after feeding in the dogfish shark (Squalus acanthias), we evaluated whether there was a corresponding net base excretion to the water at this time. In the 48 h after a natural voluntary meal (teleost tissue, averaging 5.5% of body weight), dogfish excreted 10,470 micromol kg(-1) more base (i.e. HCO3- equivalents) than the fasted control animals (which exhibited a negative base excretion of -2160 micromol kg(-1)). This large activation of branchial base excretion after feeding thereby prevented a potentially fatal alkalinization of the body fluids by the alkaline tide. The rate peaked at 330 micromol kg(-1) h(-1) at 12.5-24 h after the meal. Despite a prolonged 1.7-fold elevation in MO2 after feeding ("specific dynamic action"), urea-N excretion decreased by 39% in the same 48 h period relative to fasted controls. In contrast, ammonia-N excretion did not change appreciably. The N/O2 ratio declined from 0.51 in fasted animals to 0.19 in fed sharks, indicating a stimulation of N-anabolic processes at this time. These results, which differ greatly from those in teleost fish, are interpreted in terms of the fundamentally different ureotelic osmoregulatory strategy of elasmobranchs, and recent discoveries on base excretion and urea-retention mechanisms in elasmobranch gills.
Chris M Wood; Carol Bucking; John Fitzpatrick; Sunita Nadella
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-06-22
Journal Detail:
Title:  Respiratory physiology & neurobiology     Volume:  159     ISSN:  1569-9048     ISO Abbreviation:  Respir Physiol Neurobiol     Publication Date:  2007 Nov 
Date Detail:
Created Date:  2007-10-22     Completed Date:  2008-02-14     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101140022     Medline TA:  Respir Physiol Neurobiol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  163-70     Citation Subset:  IM    
Department of Biology, McMaster University, 1280 Main St. West, Hamilton, Ontario, Canada L8S 4K1.
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MeSH Terms
Acid-Base Equilibrium / physiology*
Ammonia / metabolism*
Analysis of Variance
Behavior, Animal
Dogfish / metabolism*
Nitrogen / metabolism*
Oxygen Consumption / physiology
Postprandial Period / physiology*
Time Factors
Water-Electrolyte Balance / physiology
Reg. No./Substance:
7664-41-7/Ammonia; 7727-37-9/Nitrogen

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