| Functional up-regulation of basolateral Na+-dependent HCO3- transporter NBCn1 in medullary thick ascending limb of K+-depleted rats. | |
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MedLine Citation:
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PMID: 15316781 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The electroneutral, Na(+)-coupled HCO(3)(-) co-transporter (NBCn1) is expressed in the basolateral membrane of rat medullary thick ascending limb (mTAL) segments and is up-regulated strongly during metabolic acidosis. We have suggested previously that NBCn1-mediated HCO(3)(-) uptake across the basolateral cell membrane is an important buffering mechanism during the transcellular transport of NH(4)(+) in the mTAL. To investigate this further we treated rats with a low-K(+) diet for 4 days, a manoeuvre known to increase proximal tubular ammoniagenesis and delivery of luminal NH(4)(+) to the mTAL. Hypokalaemia strongly increased immunolabelling of basolateral NBCn1 in the mTAL of the inner stripe of the outer medulla. Immunoblotting revealed an eightfold up-regulation of NBCn1 protein in K(+)-depleted rats. Subsequently we used in vitro perfusion of isolated mTAL and BCECF imaging to investigate Na(+)-coupled HCO(3)(-) influx in normal and K(+)-depleted rats. Hypokalaemia induced a threefold up-regulation of Na(+)-coupled HCO(3)(-) influx (1.64+/-0.28 vs. 0.47+/-0.05 pH units/minute, n=8). The Na(+)-dependent alkalinization was also significantly larger in K(+)-depleted rats (0.38+/-0.04 vs. 0.23+/-0.03 pH units). These data indicate that K(+)-depleted rats respond with a strong up-regulation of NBCn1 protein and function, probably to cope with the higher tubular load of NH(4)(+), and strengthen our previous suggestion that NBCn1 is an important player in the excretion of NH(4)(+). They also indicate that it is the delivery of luminal NH(4)(+) rather than systemic changes of pH that determine the expression of NBCn1. |
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Authors:
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Jakob K Jakobsen; Elvin Odgaard; Weidong Wang; Marie Louise Elkjaer; Søren Nielsen; Christian Aalkjaer; Jens Leipziger |
Publication Detail:
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Type: In Vitro; Journal Article; Research Support, Non-U.S. Gov't Date: 2004-08-13 |
Journal Detail:
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Title: Pflügers Archiv : European journal of physiology Volume: 448 ISSN: 0031-6768 ISO Abbreviation: Pflugers Arch. Publication Date: 2004 Sep |
Date Detail:
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Created Date: 2004-11-01 Completed Date: 2005-06-28 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0154720 Medline TA: Pflugers Arch Country: Germany |
Other Details:
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Languages: eng Pagination: 571-8 Citation Subset: IM |
Affiliation:
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Institute of Physiology, University of Aarhus, Olé Worms Allé 160, 8000 Aarhus C, Denmark. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Bicarbonates / metabolism Blotting, Western Diet Female Immunohistochemistry Kidney Medulla / metabolism* Loop of Henle / metabolism* Potassium / metabolism* Quaternary Ammonium Compounds / metabolism* Rats Rats, Wistar Sodium-Bicarbonate Symporters / biosynthesis* Up-Regulation |
| Chemical | |
Reg. No./Substance:
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0/Bicarbonates; 0/Quaternary Ammonium Compounds; 0/Slc4a4 protein, rat; 0/Sodium-Bicarbonate Symporters; 7440-09-7/Potassium |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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