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Peptides Homologous to Extracellular Loop Motifs of Connexin 43 Reversibly Abolish Rhythmic Contractile Activity in Rabbit Arteries

Peptides Homologous to Extracellular Loop Motifs of Connexin 43 Reversibly Abolish Rhythmic... 1 Phenylephrine (10 μM) evoked rises in tension in isolated rings of endothelium‐denuded rabbit superior mesenteric artery. These increases consisted of a tonic component with superimposed rhythmic activity, the frequency of which generally remained constant over time but whose amplitude exhibited cycle‐to‐cycle variability. 2 The amplitude, but not the frequency, of the rhythmic activity was affected by a series of short peptides possessing sequence homology with extracellular loops 1 and 2 of connexin 43 (Cx43). Oscillatory behaviour was abolished at concentrations of 100–300 μM (IC50 of 20–30 μM), without change in average tone. No synergy was evident between peptides corresuponding to the extracellular loops, and cytoplasmic loop peptides were biologically inactive. 3 The putative gap junction inhibitor heptanol mimicked the action of the extracellular loop peptides and abolished rhythmic activity at concentrations of 100–300 μM without effects on frequency. However, in marked contrast to the peptides, heptanol completely inhibited the contraction evoked by phenylephrine (IC50, 283 ± 28 μM). 4 The presence of mRNA encoding Cx32, Cx40 and Cx43 was detected in the rabbit superior mesenteric artery by reverse transcriptase‐polymerase chain reaction. Western blot analysis showed that Cx43 was the major connexin in the endothelium‐denuded vessel wall. 5 We conclude that intercellular communication between vascular smooth muscle cells via gap junctions is essential for synchronized rhythmic activity in isolated arterial tissue, whereas tonic force development appears to be independent of cell‐cell coupling. The molecular specificity of the peptide probes employed in the study suggests that the smooth muscle relaxant effects of heptanol may be non‐supecific and unrelated to inhibition of gap junctional communication. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Physiology Wiley

Peptides Homologous to Extracellular Loop Motifs of Connexin 43 Reversibly Abolish Rhythmic Contractile Activity in Rabbit Arteries

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References (40)

Publisher
Wiley
Copyright
Copyright © 1997 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0022-3751
eISSN
1469-7793
DOI
10.1111/j.1469-7793.1997.099bi.x
Publisher site
See Article on Publisher Site

Abstract

1 Phenylephrine (10 μM) evoked rises in tension in isolated rings of endothelium‐denuded rabbit superior mesenteric artery. These increases consisted of a tonic component with superimposed rhythmic activity, the frequency of which generally remained constant over time but whose amplitude exhibited cycle‐to‐cycle variability. 2 The amplitude, but not the frequency, of the rhythmic activity was affected by a series of short peptides possessing sequence homology with extracellular loops 1 and 2 of connexin 43 (Cx43). Oscillatory behaviour was abolished at concentrations of 100–300 μM (IC50 of 20–30 μM), without change in average tone. No synergy was evident between peptides corresuponding to the extracellular loops, and cytoplasmic loop peptides were biologically inactive. 3 The putative gap junction inhibitor heptanol mimicked the action of the extracellular loop peptides and abolished rhythmic activity at concentrations of 100–300 μM without effects on frequency. However, in marked contrast to the peptides, heptanol completely inhibited the contraction evoked by phenylephrine (IC50, 283 ± 28 μM). 4 The presence of mRNA encoding Cx32, Cx40 and Cx43 was detected in the rabbit superior mesenteric artery by reverse transcriptase‐polymerase chain reaction. Western blot analysis showed that Cx43 was the major connexin in the endothelium‐denuded vessel wall. 5 We conclude that intercellular communication between vascular smooth muscle cells via gap junctions is essential for synchronized rhythmic activity in isolated arterial tissue, whereas tonic force development appears to be independent of cell‐cell coupling. The molecular specificity of the peptide probes employed in the study suggests that the smooth muscle relaxant effects of heptanol may be non‐supecific and unrelated to inhibition of gap junctional communication.

Journal

The Journal of PhysiologyWiley

Published: Aug 1, 1997

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