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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
10
pubmed:dateCreated
2006-11-2
pubmed:abstractText
Final urinary acidification is achieved by electrogenic vacuolar H(+)-ATPases expressed in acid-secretory intercalated cells (ICs) in the connecting tubule (CNT) and the cortical (CCD) and initial medullary collecting duct (MCD), respectively. Electrogenic Na(+) reabsorption via epithelial Na(+) channels (ENaCs) in the apical membrane of the segment-specific CNT and collecting duct cells may promote H(+)-ATPases-mediated proton secretion by creating a more lumen-negative voltage. The exact localization where this supposed functional interaction takes place is unknown. We used several mouse models performing renal clearance experiments and assessed the furosemide-induced urinary acidification. Increasing Na(+) delivery to the CNT and CCD by blocking Na(+) reabsorption in the thick ascending limb with furosemide enhanced urinary acidification and net acid excretion. This effect of furosemide was abolished with amiloride or benzamil blocking ENaC action. In mice deficient for the IC-specific B1 subunit of the vacuolar H(+)-ATPase, furosemide led to only a small urinary acidification. In contrast, in mice with a kidney-specific inactivation of the alpha subunit of ENaC in the CCD and MCD, but not in the CNT, furosemide alone and in combination with hydrochlorothiazide induced normal urinary acidification. These results suggest that the B1 vacuolar H(+)-ATPase subunit is necessary for the furosemide-induced acute urinary acidification. Loss of ENaC channels in the CCD and MCD does not affect this acidification. Thus, functional expression of ENaC channels in the CNT is sufficient for furosemide-stimulated urinary acidification and identifies the CNT as a major segment in electrogenic urinary acidification.
pubmed:commentsCorrections
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0085-2538
pubmed:author
pubmed:issnType
Print
pubmed:volume
70
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1706-16
pubmed:meshHeading
pubmed-meshheading:16985514-Acid-Base Equilibrium, pubmed-meshheading:16985514-Amiloride, pubmed-meshheading:16985514-Animals, pubmed-meshheading:16985514-Diuretics, pubmed-meshheading:16985514-Epithelial Sodium Channel, pubmed-meshheading:16985514-Furosemide, pubmed-meshheading:16985514-Gene Expression Regulation, pubmed-meshheading:16985514-Gene Expression Regulation, Enzymologic, pubmed-meshheading:16985514-Hydrochlorothiazide, pubmed-meshheading:16985514-Hydrogen-Ion Concentration, pubmed-meshheading:16985514-Kidney Tubules, Collecting, pubmed-meshheading:16985514-Kidney Tubules, Distal, pubmed-meshheading:16985514-Metabolic Clearance Rate, pubmed-meshheading:16985514-Mice, pubmed-meshheading:16985514-Mice, Knockout, pubmed-meshheading:16985514-Nephrons, pubmed-meshheading:16985514-Proton-Translocating ATPases, pubmed-meshheading:16985514-Water-Electrolyte Balance
pubmed:year
2006
pubmed:articleTitle
The connecting tubule is the main site of the furosemide-induced urinary acidification by the vacuolar H+-ATPase.
pubmed:affiliation
1Institute of Physiology and Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't