| Dietary K+ restriction upregulates total and Sch-28080-sensitive bicarbonate absorption in rat tIMCD. | |
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MedLine Citation:
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PMID: 9755126 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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In tubules from the terminal segment of the inner medullary collecting duct (tIMCD) from rats with chronic metabolic acidosis, our laboratory has shown that bicarbonate absorption (JtCO2) is inhibited by removal of K+ from the luminal fluid or by the addition of Sch-28080 to the perfusate. The present study asked whether total and/or Sch-28080-sensitive JtCO2 is regulated by changes in systemic K+ homeostasis. Rat tIMCD tubules were perfused in vitro in symmetrical, HCO-3/CO2-buffered solutions containing 10 mM KCl + 6 mM NH4Cl. Total and Sch-28080-sensitive JtCO2 were measured in rats with varying K+ intake. In K+-replete rats, baseline JtCO2 was 2.1 +/- 0.3 pmol . mm-1 . min-1 (n = 6). In rats fed a K+-deficient diet for 3 days, JtCO2 was 5.4 +/- 0.7 pmol . mm-1 . min-1 (n = 16, P < 0. 05). To determine the mechanism for the increase in HCO-3 absorption observed with K+ restriction, the Sch-28080-sensitive component of JtCO2 was measured in each treatment group. Following the addition of Sch-28080 (10 microM) to the perfusate, a 40% reduction in JtCO2 was observed in K+-restricted rats. JtCO2 was not reduced following the addition of Sch-28080 in rats with normal K+ intake. Because Sch-28080-sensitive JtCO2 was increased in K+-restricted rats, Sch-28080-sensitive JtCO2 was studied further in tIMCD tubules from rats in this treatment group. In K+-restricted rats, JtCO2 decreased by 20% following the addition of 5 mM ouabain to the perfusate. This ouabain-induced decline in JtCO2 was observed both in the presence and in the absence of Sch-28080. We conclude that total and Sch-28080-sensitive net acid secretion is increased with dietary K+ restriction. However, since approximately 50% of JtCO2 is insensitive to both Sch-28080 and ouabain, future studies will be necessary to define other mechanisms of luminal acidification in the rat tIMCD. |
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Authors:
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S M Wall; P Mehta; T D DuBose |
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Publication Detail:
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Type: In Vitro; Journal Article; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: The American journal of physiology Volume: 275 ISSN: 0002-9513 ISO Abbreviation: Am. J. Physiol. Publication Date: 1998 Oct |
Date Detail:
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Created Date: 1998-11-19 Completed Date: 1998-11-19 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: F543-9 Citation Subset: IM |
Affiliation:
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University of Texas Medical School at Houston, Houston, Texas 77030, USA. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Absorption Adenosine Triphosphatases / antagonists & inhibitors Animals Bicarbonates / metabolism* Diet Enzyme Inhibitors / pharmacology Imidazoles / pharmacology Kidney Medulla / drug effects, physiology*, physiopathology Kidney Tubules, Collecting / drug effects, physiology*, physiopathology Male Potassium / pharmacology* Potassium Deficiency / physiopathology* Rats |
| Grant Support | |
ID/Acronym/Agency:
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DK-30603/DK/NIDDK NIH HHS; DK-46493/DK/NIDDK NIH HHS; DK-52935/DK/NIDDK NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Bicarbonates; 0/Enzyme Inhibitors; 0/Imidazoles; 7440-09-7/Potassium; 76081-98-6/Sch 28080; EC 3.6.1.-/Adenosine Triphosphatases |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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