A remark on the high-conductance calcium-activated potassium channel in human endothelial cells.
The patch-clamp technique was used to examine the presence of large conductance calcium-activated potassium channels (BKCa) in human endothelial cells and to characterize their properties in terms of voltage dependence, ion conduction and blockade by iberiotoxin (IbTX). Experiments were performed using cell-attached and outside-out configurations on human umbilical vein endothelial cells (HUVEC). For the experiments HUVECs, which were passaged 6-19 times, were used. In early passages channel activities were absent suggesting the appearance of BKCa depending on cell culture time. The inverse logarithmic voltage sensitivity was 10.17 mV (median) for cell-attached recordings and 12.10 mV (median) for outside-out patches (membrane voltage range: 60-120 mV, symmetrical 140 mM K+ solutions). The I/V relationship was quasilinear in the range of 0-80 mV and exhibited a nonlinear behaviour under further depolarization suggesting some kind of saturation mechanism. Using a sigmoid function to fit the data, channel conductance was calculated as 172.9 pS (median) for cell-attached patches and as 262.1 pS (median) for outside-out patches. IbTX, known as one of the most selective blockers of BKCa was perfused to outside-out patches. In two out of three experiments there was complete block of the ion channel after 1 min.
Kestler
H A
HA
Department of Medicine II, University of Ulm, Germany. h.kestler@ieee.org
Janko
S
S
Häussler
U
U
Muche
R
R
Hombach
V
V
Höher
M
M
Wiecha
J
J
D002478:Cells, Cultured; D016009:Chi-Square Distribution; D004730:Endothelium, Vascular / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D014471:Umbilical Veins / Q000166:cytology*
D010455:Peptides; D015221:Potassium Channels; C064719:iberiotoxin