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Microvascular endothelial cells from human omentum lack an inward rectifier K+ current
H M Himmel1, U Rauen, U Ravens
1Institute of Pharmacology and Toxicology, Faculty of Medicine Carl Gustav Carus, Technical University, Dresden, Germany.
Physiological Research
|February 7, 2002
Summary
Microvascular endothelial cells (EC) from human omentum lack the inwardly rectifying K+ current (I(K1)) typically found in macrovascular EC. Resting membrane potential in these cells is influenced by Na+ and Cl- currents, alongside K+ outward currents.
Area of Science:
- Endothelial cell physiology
- Ion channel function
- Cardiovascular research
Background:
- Resting membrane potential in macrovascular endothelial cells (EC) is primarily determined by the inwardly rectifying K+ current (I(K1)).
- The presence and role of I(K1) in microvascular EC are variable and not fully understood.
- Human omentum microvascular EC were investigated to clarify the contribution of I(K1) to their resting membrane potential.
Purpose of the Study:
- To investigate the presence and function of inwardly rectifying K+ current (I(K1)) in human omentum microvascular endothelial cells (EC).
- To determine the ion channel mechanisms underlying the resting membrane potential in these microvascular EC.
- To compare ion channel activity in microvascular EC with that of macrovascular EC.
Main Methods:
- Voltage-clamp technique applied to cultured microvascular EC from human omentum.
- Comparison with macrovascular EC from human iliac artery and bovine aorta.
- Assessment of current-voltage relations, ion sensitivity (K+, Ba2+, Na+, Cl-), and channel blockers (tetraethylammonium).
Main Results:
- Human omentum EC exhibited an outwardly rectifying current-voltage relation.
- Inward currents were insensitive to extracellular K+ and Ba2+ block, indicating a lack of I(K1).
- Extracellular Na+ and Cl- influenced the current-voltage relation, suggesting their contribution to basal current. Tetraethylammonium reduced outward current, and Ca2+-activated K+ current was suggested.
- In contrast, EC from human iliac artery and bovine aorta showed Ba2+-sensitive, inwardly rectifying currents dependent on extracellular K+.
Conclusions:
- Human omentum microvascular EC lack the inwardly rectifying K+ current (I(K1)) characteristic of macrovascular EC.
- Resting membrane potential in human omentum EC is likely determined by Na+ and Cl- currents, in addition to K+ outward currents.
- This study highlights distinct ion transport mechanisms in microvascular versus macrovascular endothelial cells.