Characterization of Volume-activated Chloride Currents in Endothelial Cells from Bovine Pulmonary Artery |
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Authors: | G Szücs G Buyse J Eggermont G Droogmans B Nilius |
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Institution: | (1) KU Leuven, Laboratorium voor Fysiologie, Campus Gasthuisberg, B-3000 LEUVEN, Belgium, BE |
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Abstract: | We have measured the kinetic and pharmacological properties of volume-activated Cl− currents (I
Cl,vol) in endothelial cells, and tried to correlate them with those of the already described volume-activated current I
Cln. Both conductances show a similar permeability sequence for monovalent anions, and they are blocked by extracellular ATP.
In the present report, we demonstrate by Western blot and RT-PCR that cultured endothelial cells from bovine pulmonary artery
(CPAE) contain pI
Cln. The expression of this protein has been shown to be closely associated with the I
Cln current.
I
Cl,vol showed however, in contrast with I
Cln, no striking inactivation at positive potentials. This property is also at variance with that of the volume-activated current
related to MDR-1. Activation of I
Cl,vol at potentials more negative than −80 mV was not time dependent, which excludes a major contribution of a ClC-2 related current.
The antiviral nucleoside analogue AZT (3′-azido-3′-deoxythymidine) inhibited I
Cl,vol by 21 ± 2.7% (n = 10), at a concentration of 100 μm. Another antiviral drug, acyclovir (ACV, 9-(2-hydroxyethoxy)methyl]guanine) blocked I
Cl,vol by 27 ± 6.2% at 100 μm (n = 11). Both blocking effects are much smaller than those reported for I
Cln.
The phenol derivative gossypol, which blocks I
Cln-related currents, efficiently inhibited I
Cl,vol in CPAE cells (67 ± 2.1% at 1 μm, n = 7, K
I
= 0.4 μm).
The presence of pI
Cln in CPAE cells and the similar qualitative pharmacological profile of I
Cl,vol and I
Cln support the hypothesis that pI
Cln is a good molecular candidate for I
Cl,vol in endothelial cells. The discrepant kinetic properties may indicate that these time-dependent currents at high positive
or negative potentials are not intrinsic properties of the channels, but are caused by time-dependent depletion/accumulation
phenomena due to the large amplitudes of these currents.
Received: 8 May 1995/Revised: 12 October 1995 |
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Keywords: | : Endothelial cells — Volume-activated Cl− currents — ICln— Nucleosides — Gossypol |
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