Microvascular
Endothelial Cells from Human Omentum Lack an
Inward Rectifier K+ Current
H. M.
HIMMEL1, U. RAUEN2, U.
RAVENS1
1Institute of
Pharmacology and Toxicology, Faculty of Medicine
Carl Gustav Carus, Technical University, Dresden
and 2Institute of
Physiological Chemistry, University of Essen,
Germany
Received
December 8, 2000
Accepted March 19, 2001
Summary
In
most macrovascular endothelial cell (EC)
preparations, resting membrane potential is
determined by the inwardly rectifying K+ current
(IK1), whereas in microvascular EC the presence
of IK1 varies markedly. Cultured microvascular EC
from small vessels of human omentum were examined
by means of the voltage-clamp technique to
elucidate the putative role of IK1 in maintaining
resting membrane potential. Macrovascular EC from
human iliac artery and bovine aorta served as
reference. Human omentum EC showed an outwardly
rectifying current-voltage relation. Inward
current was hardly sensitive to variations of
extracellular [K+] and Ba2+ block suggesting lack
of IK1. However, substitution of extracellular
[Na+] and/or [Cl-] affected the current-voltage
relation indicating that Na+ and Cl- contribute
to basal current. Furthermore, outward current
was reduced by tetraethylammonium (10 mM), and
cell-attached recordings suggested the presence
of a Ca2+-activated K+ current. In contrast to
human omentum EC, EC from human iliac artery and
bovine aorta possessed inwardly rectifying
currents which were sensitive to variations of
extracellular [K+] and blocked by Ba2+. Thus, the
lack of IK1 in human omentum EC suggests that
resting membrane potential is determined by Na+
and Cl- currents in addition to K+ outward
currents.
Key words
Whole-cell
voltage clamp · Ion substitution
· Non-excitable cells · Na+ background current · Chloride conductance · Ca2+-activated K+ current
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requests
Prof.
Dr. Ursula Ravens, Institut für Pharmakologie
und Toxikologie, Medizinische Facultät Carl
Gustav Carus, TU Dresden, Fetscherstr. 74,
D-01307 Dresden, Germany. Fax: 49-351-4586315,
E-mail: ravens@rcs.urz.tu-dresden.de
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