Mechanisms of H+/HCO3- transport in the medullary thick ascending limb of rat kidney.
Details
Serval ID
serval:BIB_CD2A5EC0ECEA
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Mechanisms of H+/HCO3- transport in the medullary thick ascending limb of rat kidney.
Journal
Kidney international. Supplement
ISSN
0098-6577 (Print)
ISSN-L
0098-6577
Publication state
Published
Issued date
07/1991
Peer-reviewed
Oui
Volume
33
Pages
S43-6
Language
english
Notes
Publication types: Journal Article
Publication Status: ppublish
Publication Status: ppublish
Abstract
The rat MTAL secretes protons into the tubular fluid and thus absorbs bicarbonate at substantial rates. Yet the cellular mechanisms of H+/HCO3- transport in the rat MTAL remain largely unsettled. We have performed intracellular pH recovery studies with use of the fluorescent probe BCECF in suspensions of rat MTAL fragments. Luminal H+ secretion occurs by two mechanisms (each responsible for 50% of the normal pHi recovery rate): (1) an electroneutral Na+/H+ antiporter that has an Na-Km of about 11 mM and is inhibited by amiloride (Ki = 2.8 x 10(-5) M); (2) a primary H+ pump that is inhibited by 10(-4) M NEM and 10(-4) M omeprazole, but not by 10(-4) M vanadate or removal of external K. These results suggest the presence of a vacuolar H(+)-ATPase rather than a H(+)-K(+)-ATPase. Basolateral HCO3 exit occurs predominantly by a Cl(-)- and Na(+)-independent electroneutral K+/HCO3- symporter, that has an HCO3-Km of about 17 mM, and is partially inhibited by 10(-4) M DIDS. Basolateral HCO3- efflux was not accompanied by variations of membrane potential monitored with the Em-sensitive fluorescent probe DIS-C3-5, and was not affected by maneuvers that depolarize the cells. It was strongly inhibited by cellular K depletion and dependent on transmembrane K gradient. We conclude that the rat MTAL should secrete protons through both Na+/H+ antiporter and H(+)-ATPase, and that basolateral HCO3- exit should occur through an electroneutral K+/HCO3- symporter.
Keywords
Bicarbonates/metabolism, Biological Transport, Carrier Proteins/metabolism, Electrochemistry, Hydrogen-Ion Concentration, In Vitro Techniques, Kidney Medulla, Loop of Henle/metabolism, Proton-Translocating ATPases/metabolism, Sodium-Hydrogen Exchangers
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Create date
03/03/2016 17:49
Last modification date
14/04/2023 14:08