Characterization of the Stretch-activated Chloride Channel in Isolated Human Atrial Myocytes |
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| Authors: | R Sato S-i Koumi |
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| Institution: | (1) Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, 303 East Chicago Avenue, Chicago, IL 60611, USA, US;(2) First Department of Medicine, Nippon Medical School, Tokyo 113, Japan, JP |
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| Abstract: | Macroscopic and unitary currents through stretch-activated Cl− channels were examined in isolated human atrial myocytes using whole-cell, excised outside-out and inside-out configurations
of the patch-clamp technique. When K+ and Ca2+ conductances were blocked and the intracellular Ca2+ concentration (Ca2+]
i
) was reduced, application of positive pressure via the pipette activated membrane currents under whole-cell voltage-clamp
conditions. The reversal potential of the current shifted by 60 mV per 10-fold change in the external Cl− concentration, indicating that the current was Cl− selective. The current was inhibited by bath application of 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) and
9-anthracenecarboxylic acid (9-AC). β-Adrenergic stimulation failed to activate a Cl− current. In single channel recordings from outside-out patches, positive pressure in the pipette activated the unitary current
with half-maximal activation of 14.7 mm Hg at +40 mV. The current-voltage relationship of single channel activity obtained
in inside-out patches was linear in symmetrical Cl− solution with the averaged slope conductance of 8.6 ± 0.7 pS (mean ±sd, n= 10). The reversal potential shift of the channel by changing Cl− concentration was consistent with a Cl− selective channel. The open time distribution was best described by a single exponential function with mean open lifetime
of 80.4 ± 9.6 msec (n= 9), while at least two exponentials were required to fit the closed time distributions with a time constant for the fast
component of 11.5 ± 2.2 msec (n= 9) and that for the slow component of 170.2 ± 21.8 msec (n= 9). Major changes in the single channel activity in response to pressure were caused by changes in the interburst interval.
Single channel activity was inhibited by DIDS and 9-AC in a manner similar to whole-cell configuration. These results suggest
that membrane stretch induced by applying pressure via the pipette activated a Cl− current in human atrial myocytes. The current was sensitive to Cl− channel blockers and exhibited membrane voltage-independent bursting opening without sensitive to β-adrenergic stimulation.
Received: 21 October 1996/Revised: 17 December 1997 |
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| Keywords: | : Patch-clamp technique — Stretch-activated Cl− channel — Human atrial myocytes |
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