Single-Channel Characterization of the Pharmacological Properties of the K(Ca2+) Channel of Intermediate Conductance in Bovine Aortic Endothelial Cells

Single-Channel Characterization of the Pharmacological Properties of the K(Ca2+) Channel of... The pharmacological profile of a voltage-independent Ca2+-activated potassium channel of intermediate conductance (IK(Ca2+)) present in bovine aortic endothelial cells (BAEC) was investigated in a series of inside-out and outside-out patch-clamp experiments. Channel inhibition was observed in response to external application of ChTX with a half inhibition concentration of 3.3 ± 0.3 nm (n= 4). This channel was insensitive to IbTX, but channel block was detected following external application of MgTX and StK leading to the rank order toxin potency ChTX > StK > MgTX >>IbTX. A reduction of the channel unitary current amplitude was also measured in the presence of external TEA, with half reduction occurring at 23 ± 3 mm TEA (n= 3). The effect of TEA was voltage insensitive, an indication that TEA may bind to a site located on external side of the pore region of this channel. Similarly, the addition of d-TC to the external medium caused a reduction of the channel unitary current amplitude with half reduction at 4.4 ± 0.3 mm (n= 4). In contrast, application of d-TC to the bathing medium in inside-out experiments led to the appearance of long silent periods, typical of a slow blocking process. Finally, the IK(Ca2+) in BAEC was found to be inhibited by NS1619, an activator of the Ca2+-activated potassium channel of large conductance (Maxi K(Ca2+)), with a half inhibition value of 11 ± 0.8 μm (n= 4). These results provide evidence for a pharmacological profile distinct from that reported for the Maxi K(Ca2+) channel, with some features attributed to the voltage-gated KV1.2 potassium channel. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Single-Channel Characterization of the Pharmacological Properties of the K(Ca2+) Channel of Intermediate Conductance in Bovine Aortic Endothelial Cells

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 1998 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900379
Publisher site
See Article on Publisher Site

Abstract

The pharmacological profile of a voltage-independent Ca2+-activated potassium channel of intermediate conductance (IK(Ca2+)) present in bovine aortic endothelial cells (BAEC) was investigated in a series of inside-out and outside-out patch-clamp experiments. Channel inhibition was observed in response to external application of ChTX with a half inhibition concentration of 3.3 ± 0.3 nm (n= 4). This channel was insensitive to IbTX, but channel block was detected following external application of MgTX and StK leading to the rank order toxin potency ChTX > StK > MgTX >>IbTX. A reduction of the channel unitary current amplitude was also measured in the presence of external TEA, with half reduction occurring at 23 ± 3 mm TEA (n= 3). The effect of TEA was voltage insensitive, an indication that TEA may bind to a site located on external side of the pore region of this channel. Similarly, the addition of d-TC to the external medium caused a reduction of the channel unitary current amplitude with half reduction at 4.4 ± 0.3 mm (n= 4). In contrast, application of d-TC to the bathing medium in inside-out experiments led to the appearance of long silent periods, typical of a slow blocking process. Finally, the IK(Ca2+) in BAEC was found to be inhibited by NS1619, an activator of the Ca2+-activated potassium channel of large conductance (Maxi K(Ca2+)), with a half inhibition value of 11 ± 0.8 μm (n= 4). These results provide evidence for a pharmacological profile distinct from that reported for the Maxi K(Ca2+) channel, with some features attributed to the voltage-gated KV1.2 potassium channel.

Journal

The Journal of Membrane BiologySpringer Journals

Published: May 15, 1998

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