Properties of a constitutively active Ca2+-permeable non-selective cation channel in rabbit ear artery myocytes
In smooth muscle, non-selective cation conductances contribute to agonist-evoked depolarisation and contraction, and in the present study using patch-pipette techniques we describe the properties of a constitutively active cation channel. With whole-cell recording in K + -free conditions, there was...
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Published in | The Journal of physiology Vol. 549; no. 1; pp. 143 - 156 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Oxford, UK
The Physiological Society
15.05.2003
Blackwell Publishing Ltd Blackwell Science Inc |
Subjects | |
Online Access | Get full text |
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Summary: | In smooth muscle, non-selective cation conductances contribute to agonist-evoked depolarisation and contraction, and in the
present study using patch-pipette techniques we describe the properties of a constitutively active cation channel. With whole-cell
recording in K + -free conditions, there was a spontaneous current with a reversal potential ( E r ) that was altered by replacement of external Na + by an impermeant cation, but not when external Cl â was replaced by an impermeant anion. The tonic cation inward current could be carried by Ca 2+ ions and was greatly enhanced when the external Ca 2+ concentration was reduced. In outside-out patches there was spontaneous cation channel activity that could be resolved into
three conductance states of about 15, 25 and 40 pS, all with the same E r as the whole-cell current. Kinetic analysis revealed that there were two open times of about 1 and 5 ms and that the currents
displayed bursting kinetics with burst durations of approximately 5 ms and 25 ms. Removal of external Ca 2+ ions increased the probability of channel opening ( P o ) sixfold, which was associated with an increase in the longer burst duration. Bath application of the diacylglycerol analogue
1-oleoyl-2-acetyl- sn -glycerol increased P o , but phorbol 12,13-dibutyrate, which stimulates protein kinase C (PKC), reduced channel activity. In contrast, the PKC inhibitor
chelerythrine increased the activity of channel currents. It is concluded that in rabbit ear artery myocytes there is a constitutively
active Ca 2+ -permeable cation channel that is regulated by external Ca 2+ ions and suppressed by tonic PKC activity. It is proposed that this mechanism may contribute to the resting membrane conductance
and basal Ca 2+ influx in this particular arterial preparation. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0022-3751 1469-7793 |
DOI: | 10.1113/jphysiol.2002.038190 |