Ca 2+ -Induced Cl− Efflux at Rat Distal Colonic Epithelium

Ca 2+ -Induced Cl− Efflux at Rat Distal Colonic Epithelium With the aid of the halide-sensitive dye 6-methoxy-N-ethylquinolinium iodide (MEQ), changes in intracellular Cl- concentration were measured to characterize the role of Ca2+-dependent Cl- channels at the rat distal colon. In order to avoid indirect effects of secretagogues mediated by changes in the driving force for Cl- exit (i.e., mediated by opening of Ca2+-dependent K+ channels), all experiments were performed under depolarized conditions, i.e., in the presence of high extracellular K+ concentrations. The Ca2+-dependent secretagogue carbachol induced a stilbene-sensitive Cl- efflux, which was mimicked by the Ca2+ ionophore ionomycin. Surprisingly, the activation of Ca2+-dependent Cl- efflux was resistant against blockers of classical Ca2+ signaling pathways such as phospholipase C, protein kinase C and calmodulin. Hence, alternative pathways must be involved in the signaling cascade. One possible signaling molecule seems to be nitric oxide (NO) as the NO donor sodium nitroprusside could induce Cl- efflux. Vice versa, the NO synthase inhibitor N-ω-monomethyl-arginine (l-NMMA) reduced the carbachol-induced Cl- efflux. This indicates that NO may be involved in part of the signaling cascade. In order to test the ability of the epithelium to produce NO, the expression of different isoforms of NO synthase was verified by immunohistochemistry. In addition, the cytoskeleton seems to play a role in the activation of Ca2+-dependent Cl- channels. Inhibitors of microtubule association such as nocodazole and colchicine as well as jasplakinolide, a drug that enhances actin polymerization, inhibited the carbachol-induced Cl- efflux. Consequently, the activation of apical Cl- channels by muscarinic receptor stimulation differs in signal transduction from the classical phospholipase C/protein kinase C way. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Ca 2+ -Induced Cl− Efflux at Rat Distal Colonic Epithelium

Loading next page...
 
/lp/springer_journal/ca-2-induced-cl-efflux-at-rat-distal-colonic-epithelium-eyebxv1TFI
Publisher
Springer Journals
Copyright
Copyright © 2008 by Springer Science+Business Media, LLC
Subject
Life Sciences; Human Physiology ; Biochemistry, general
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-007-9078-0
Publisher site
See Article on Publisher Site

Abstract

With the aid of the halide-sensitive dye 6-methoxy-N-ethylquinolinium iodide (MEQ), changes in intracellular Cl- concentration were measured to characterize the role of Ca2+-dependent Cl- channels at the rat distal colon. In order to avoid indirect effects of secretagogues mediated by changes in the driving force for Cl- exit (i.e., mediated by opening of Ca2+-dependent K+ channels), all experiments were performed under depolarized conditions, i.e., in the presence of high extracellular K+ concentrations. The Ca2+-dependent secretagogue carbachol induced a stilbene-sensitive Cl- efflux, which was mimicked by the Ca2+ ionophore ionomycin. Surprisingly, the activation of Ca2+-dependent Cl- efflux was resistant against blockers of classical Ca2+ signaling pathways such as phospholipase C, protein kinase C and calmodulin. Hence, alternative pathways must be involved in the signaling cascade. One possible signaling molecule seems to be nitric oxide (NO) as the NO donor sodium nitroprusside could induce Cl- efflux. Vice versa, the NO synthase inhibitor N-ω-monomethyl-arginine (l-NMMA) reduced the carbachol-induced Cl- efflux. This indicates that NO may be involved in part of the signaling cascade. In order to test the ability of the epithelium to produce NO, the expression of different isoforms of NO synthase was verified by immunohistochemistry. In addition, the cytoskeleton seems to play a role in the activation of Ca2+-dependent Cl- channels. Inhibitors of microtubule association such as nocodazole and colchicine as well as jasplakinolide, a drug that enhances actin polymerization, inhibited the carbachol-induced Cl- efflux. Consequently, the activation of apical Cl- channels by muscarinic receptor stimulation differs in signal transduction from the classical phospholipase C/protein kinase C way.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Jan 24, 2008

References

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