Volume 50, Issue 6:

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

Reprint 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

PHYSIOLOGICAL RESEARCH
© 2001 by the Institute of Physiology,
Czech Academy of Sciences

ISSN 0862 - 8408

Issue 6