| Urea transport processes are induced in rat IMCD subsegments when urine concentrating ability is reduced. | |
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MedLine Citation:
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PMID: 9887081 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Infusing urea into low-protein-fed mammals increases urine concentration within 5-10 min. To determine which urea transporter may be responsible, we measured urea transport in perfused IMCD3 segments [inner medullary collecting duct (IMCD) segments from the deepest third of the IMCD] from low-protein-fed rats. Basal facilitated urea permeability increased 78%, whereas active urea secretion was completely inhibited. This suggests that upregulation of facilitated urea transport may mediate the rapid increase in urine concentration. Next, expression of active urea transporter(s) in perfused IMCDs was determined in rats with other causes of reduced urine concentrating ability. In untreated and water diuretic rats, IMCD1 segments showed no active urea transport, nor did IMCD2 segments from untreated or hypercalcemic rats. In IMCD1 segments from hypercalcemic rats, active urea reabsorption was induced. The induced active urea reabsorption was completely inhibited by replacing perfusate Na+ with N-methyl-D-glucamine (NMDG+). Active urea secretion was completely inhibited in IMCD3 segments from hypercalcemic rats. In contrast, water diuresis stimulated active urea secretion in IMCD2 segments. The induced active urea secretion was inhibited by phloretin, ouabain, triamterene, or replacing perfusate Na+ with NMDG+. In conclusion, the response of active urea transporters to reductions in urine concentrating ability follows two paradigms: one occurs with hypercalcemia or a low-protein diet, and the second occurs only in water diuresis. |
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Authors:
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A Kato; J M Sands |
Publication Detail:
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Type: In Vitro; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: The American journal of physiology Volume: 276 ISSN: 0002-9513 ISO Abbreviation: Am. J. Physiol. Publication Date: 1999 Jan |
Date Detail:
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Created Date: 1999-03-05 Completed Date: 1999-03-05 Revised Date: 2007-11-14 |
Medline Journal Info:
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Nlm Unique ID: 0370511 Medline TA: Am J Physiol Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: F62-71 Citation Subset: IM |
Affiliation:
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Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Biological Transport, Active / physiology Blood / metabolism Carbohydrates / pharmacology Carrier Proteins / drug effects, metabolism* Dietary Proteins / administration & dosage, pharmacology Diuresis / physiology Food Deprivation / physiology Hypercalcemia / metabolism Kidney Concentrating Ability / physiology* Kidney Medulla Kidney Tubules, Collecting / metabolism* Male Membrane Glycoproteins / drug effects, metabolism* Membrane Transport Proteins* Rats Rats, Sprague-Dawley Urea / metabolism Urine / chemistry |
| Grant Support | |
ID/Acronym/Agency:
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P01-DK-50268/DK/NIDDK NIH HHS; R01-DK-41707/DK/NIDDK NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Carbohydrates; 0/Carrier Proteins; 0/Dietary Proteins; 0/Membrane Glycoproteins; 0/Membrane Transport Proteins; 0/urea transporter; 57-13-6/Urea |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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