Document Detail

Renal handling of NH3/NH4+: recent concepts.
MedLine Citation:
PMID:  16113588     Owner:  NLM     Status:  MEDLINE    
To be appropriately excreted in urine, NH4+, the major component of urinary acid excretion, must be synthesized by proximal tubular cells, secreted into the proximal tubular fluid, reabsorbed by the medullary thick ascending limb (MTAL) to be accumulated in the medullary interstitium, and finally secreted in medullary collecting ducts. Several targets have been identified to account at the gene expression level for the adaptation of renal NH4+ synthesis and transport in response to a chronic acid load. These targets are the key enzymes of ammoniagenesis (mitochondrial glutaminase and glutamate dehydrogenase) and gluconeogenesis (phosphoenolpyruvate carboxykinase) and the Na+/H+(NH4+) exchanger NHE3 in the proximal tubule, the apical Na+-K+(NH4+)-2Cl- cotransporter of the MTAL, the basolateral Na+-K+(NH4+)-2Cl- cotransporter, and likely the epithelial Rh B and C glycoproteins in the collecting ducts. An acid pH per se appears to be a major factor in the control of the expression of these genes during metabolic acidosis probably through activation of pH sensors. Glucocorticoids may also act in concert with an acid pH to coordinate the adaptation of various tubular cell types. The present review focuses on some new aspects of NH3/ NH4+ transport and of regulations of gene expression that have recently emerged.
Zoubida Karim; Marta Szutkowska; Catherine Vernimmen; Maurice Bichara
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Publication Detail:
Type:  Journal Article; Review     Date:  2005-08-19
Journal Detail:
Title:  Nephron. Physiology     Volume:  101     ISSN:  1660-2137     ISO Abbreviation:  Nephron Physiol     Publication Date:  2005  
Date Detail:
Created Date:  2005-11-02     Completed Date:  2006-05-24     Revised Date:  2008-04-08    
Medline Journal Info:
Nlm Unique ID:  101159772     Medline TA:  Nephron Physiol     Country:  Switzerland    
Other Details:
Languages:  eng     Pagination:  p77-81     Citation Subset:  IM    
Copyright Information:
Copyright 2005 S. Karger AG, Basel.
INSERM U.426, IFR 2, Faculté de Médecine Xavier Bichat, Paris Cedex, France.
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MeSH Terms
Acid-Base Equilibrium / physiology*
Ammonia / metabolism*
Kidney / physiology*
Quaternary Ammonium Compounds / metabolism*
Symporters / genetics,  metabolism*
Reg. No./Substance:
0/Quaternary Ammonium Compounds; 0/Symporters; 7664-41-7/Ammonia

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