| Regulation of acidification in the rat inner medullary collecting duct. | |
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MedLine Citation:
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PMID: 1659187 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The inner medullary collecting duct (IMCD) is the most distal portion of the nephron and plays an important role in urinary net acid excretion. The terminal or distal two thirds of the IMCD is lined by a single cell type, now termed the IMCD cell, which not only secretes protons, but transports sodium and potassium and responds to many hormones. The IMCD may account for greater than 50% of the excreted acid under control conditions and, during acidosis, absolute acid secretion may increase fivefold. Conversely, during alkalemia, acid secretion by this segment is abolished. Thus, the IMCD responds appropriately to perturbations in systemic acid-base balance. Furthermore, models of renal tubular acidosis have been demonstrated along this nephron segment. Three transporters that are important in acid-base control, the Na+/H+ and the Cl-/HCO3- exchanger and an active proton pump, presumably an H(+)-adenosine phosphatase (ATPase), have been demonstrated in IMCD cells. The former two are situated in the basolateral membrane, while the latter is situated in the apical membrane. Only the proton pump is responsible for actual acid addition to the urine. The intracellular mechanisms that modulate the proton pump are just beginning to be defined. It is likely that acid secretory activity involves exocytic insertion of additional pumps, and is dependent on cell pH changes, which are the primary signal, and on changes in intracellular calcium concentration and calmodulin activity, which are the second messengers. |
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Authors:
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E A Alexander; J H Schwartz |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.; Review |
Journal Detail:
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Title: American journal of kidney diseases : the official journal of the National Kidney Foundation Volume: 18 ISSN: 0272-6386 ISO Abbreviation: Am. J. Kidney Dis. Publication Date: 1991 Nov |
Date Detail:
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Created Date: 1991-11-27 Completed Date: 1991-11-27 Revised Date: 2007-11-14 |
Medline Journal Info:
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Nlm Unique ID: 8110075 Medline TA: Am J Kidney Dis Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 612-8 Citation Subset: IM |
Affiliation:
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Thorndike Memorial Laboratory, Boston City Hospital, MA. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Acid-Base Equilibrium
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physiology* Acidosis, Renal Tubular / metabolism Animals Biological Transport, Active Carbonic Anhydrases / metabolism Carrier Proteins / metabolism Chloride-Bicarbonate Antiporters Hydrogen-Ion Concentration Kidney Concentrating Ability Kidney Tubules, Collecting / physiology* Membrane Proteins / metabolism Proton-Translocating ATPases / metabolism Second Messenger Systems / physiology Sodium-Hydrogen Antiporter |
| Grant Support | |
ID/Acronym/Agency:
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DK-28164/DK/NIDDK NIH HHS; DK-37105/DK/NIDDK NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Carrier Proteins; 0/Chloride-Bicarbonate Antiporters; 0/Membrane Proteins; 0/Sodium-Hydrogen Antiporter; EC 3.6.3.14/Proton-Translocating ATPases; EC 4.2.1.1/Carbonic Anhydrases |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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