Transcellular Chloride Pathways in Ambystoma Proximal Tubule

Transcellular Chloride Pathways in Ambystoma Proximal Tubule The transport mechanisms of Ambystoma proximal tubule that mediate transcellular Cl− absorption linked to Na+ were investigated in isolated perfused tubules using Cl−-selective and voltage-recording microelectrodes. In control solutions intracellular activity of Cl− (a i Cl ) is 11.3 ± 0.5 mm, the basolateral (V 1 ), apical (V 2 ), and transepithelial (V 3 ) potential differences are −68 ± 1.2 mV, +62 ± 1.2 mV and −6.4 ± 0.3 mV, respectively. When Na+ absorption is decreased by removal of organic substrates from the lumen, a i Cl falls by 1.3 ± 0.3 mm and V 2 hyperpolarizes by +11.4 ± 1.7 mV. Subsequent removal of Na+ from the lumen causes a i Cl to fall further by 2.3 ± 0.4 mm and V 2 to hyperpolarize further by +15.3 ± 2.4 mV. The contribution of transporters and channels to the observed changes of a i Cl was examined using ion substitutions and inhibitors. Apical Na/Cl or Na/K/2Cl symport is excluded because bumetanide, furosemide or hydrochlorothiazide have no effect on a i Cl . The effects of luminal HCO− 3 removal and/or of disulfonic stilbenes argue against the presence of apical Cl-base exchange such as Cl-HCO3 or Cl-OH. The effects of basolateral HCO− 3 removal, of basolateral Na+ removal and/or of disulfonic stilbenes are compatible with presence of basolateral Na-independent Cl-base exchange and Na-driven Cl-HCO3 exchange. Several lines of evidence favor conductive Cl− transport across both the apical and basolateral membrane. Addition of the chloride-channel blocker diphenylamine-2-carboxylate to the lumen or bath, increases the a i Cl by 2.4 ± 0.6 mm or 2.9 ± 1.0 mm respectively. Moreover, following inhibition by DIDS of all anion exchangers in HCO− 3-free Ringer, the equilibrium potential for Cl− does not differ from the membrane potential V 2 . Finally, the logarithmic changes in a i Cl in various experimental conditions correlate well with the simultaneous changes in either basolateral or apical membrane potential. These findings strongly support the presence of Cl− channels at the apical and basolateral cell membranes of the proximal tubule. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Transcellular Chloride Pathways in Ambystoma Proximal Tubule

Loading next page...
 
/lp/springer_journal/transcellular-chloride-pathways-in-ambystoma-proximal-tubule-u0VJdgWqKH
Publisher
Springer-Verlag
Copyright
Copyright © 1998 by Springer-Verlag New York Inc.
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900444
Publisher site
See Article on Publisher Site

Abstract

The transport mechanisms of Ambystoma proximal tubule that mediate transcellular Cl− absorption linked to Na+ were investigated in isolated perfused tubules using Cl−-selective and voltage-recording microelectrodes. In control solutions intracellular activity of Cl− (a i Cl ) is 11.3 ± 0.5 mm, the basolateral (V 1 ), apical (V 2 ), and transepithelial (V 3 ) potential differences are −68 ± 1.2 mV, +62 ± 1.2 mV and −6.4 ± 0.3 mV, respectively. When Na+ absorption is decreased by removal of organic substrates from the lumen, a i Cl falls by 1.3 ± 0.3 mm and V 2 hyperpolarizes by +11.4 ± 1.7 mV. Subsequent removal of Na+ from the lumen causes a i Cl to fall further by 2.3 ± 0.4 mm and V 2 to hyperpolarize further by +15.3 ± 2.4 mV. The contribution of transporters and channels to the observed changes of a i Cl was examined using ion substitutions and inhibitors. Apical Na/Cl or Na/K/2Cl symport is excluded because bumetanide, furosemide or hydrochlorothiazide have no effect on a i Cl . The effects of luminal HCO− 3 removal and/or of disulfonic stilbenes argue against the presence of apical Cl-base exchange such as Cl-HCO3 or Cl-OH. The effects of basolateral HCO− 3 removal, of basolateral Na+ removal and/or of disulfonic stilbenes are compatible with presence of basolateral Na-independent Cl-base exchange and Na-driven Cl-HCO3 exchange. Several lines of evidence favor conductive Cl− transport across both the apical and basolateral membrane. Addition of the chloride-channel blocker diphenylamine-2-carboxylate to the lumen or bath, increases the a i Cl by 2.4 ± 0.6 mm or 2.9 ± 1.0 mm respectively. Moreover, following inhibition by DIDS of all anion exchangers in HCO− 3-free Ringer, the equilibrium potential for Cl− does not differ from the membrane potential V 2 . Finally, the logarithmic changes in a i Cl in various experimental conditions correlate well with the simultaneous changes in either basolateral or apical membrane potential. These findings strongly support the presence of Cl− channels at the apical and basolateral cell membranes of the proximal tubule.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Feb 2, 2014

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off