| Renal bicarbonate reabsorption in the rat. III. Distal tubule perfusion study of load dependence and bicarbonate permeability. | |
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MedLine Citation:
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PMID: 2760220 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Using continuous microperfusion techniques, we studied the load dependence of bicarbonate reabsorption along cortical distal tubules of the rat kidney and their bicarbonate permeability. Net bicarbonate transport was evaluated from changes in tracer inulin concentrations and total CO2 measurements by microcalorimetry. Bicarbonate permeability was estimated from the flux of total CO2 along known electrochemical gradients into bicarbonate-and chloride-free perfusion solution containing 10(-4) M acetazolamide. Transepithelial potential differences were measured with conventional glass microelectrodes. Significant net bicarbonate reabsorption occurred at luminal bicarbonate levels from 5 to 25 mM, and at perfusion rates from 5 to 30 nl/min. Bicarbonate reabsorption increased in a load-dependent manner, both during increments in luminal bicarbonate concentration or perfusion rate, reaching saturation at a load of 250 pmol/min with a maximal reabsorption rate of approximately 75 pmol/min.mm. Rate of bicarbonate reabsorption was flow dependent at luminal concentrations of 10 but not at 25 mM. During chronic metabolic alkalosis, maximal rates of reabsorption were significantly reduced to 33 pmol/min.mm. The bicarbonate permeability was 2.32 +/- 0.13 x 10(-5) cm/s in control rats, and 2.65 +/- 0.26 x 10(-5) cm/s in volume-expanded rats. Our data indicate that at physiological bicarbonate concentrations in the distal tubule passive bicarbonate fluxes account for only 16-21% of net fluxes. At high luminal bicarbonate concentrations, passive bicarbonate reabsorption contributes moderately to net reabsorption of this anion. |
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Authors:
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Y L Chan; G Malnic; G Giebisch |
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. |
Journal Detail:
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Title: The Journal of clinical investigation Volume: 84 ISSN: 0021-9738 ISO Abbreviation: J. Clin. Invest. Publication Date: 1989 Sep |
Date Detail:
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Created Date: 1989-09-21 Completed Date: 1989-09-21 Revised Date: 2009-11-18 |
Medline Journal Info:
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Nlm Unique ID: 7802877 Medline TA: J Clin Invest Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 931-8 Citation Subset: AIM; IM; S |
Affiliation:
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Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Absorption Acid-Base Equilibrium Animals Bicarbonates / administration & dosage, metabolism* Biological Transport, Active Blood Flow Velocity Capillary Permeability* Kidney Cortex / blood supply, metabolism, physiology Kidney Tubules / metabolism* Kidney Tubules, Distal / blood supply, metabolism*, physiology Male Perfusion* Rats Rats, Inbred Strains |
| Grant Support | |
ID/Acronym/Agency:
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AM-17433/AM/NIADDK NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Bicarbonates |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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