Electrogenic Na+/K(+)-transport in human endothelial cells

Area of Science:

• Physiology
• Cell Biology
• Biophysics

Background:

• The Na+/K+ pump (sodium-potassium adenosine triphosphatase) is crucial for maintaining cellular ion gradients and membrane potential.
• Endothelial cells play a vital role in vascular function, and their ion transport mechanisms are of significant interest.

Purpose of the Study:

• To characterize the electrophysiological properties of the Na+/K+ pump in human umbilical cord vein endothelial cells.
• To investigate the effects of intracellular sodium, extracellular potassium, and dihydroouabain on Na+/K+ pump currents.

Main Methods:

• Whole-cell and nystatin-perforated-patch-clamp techniques were employed to measure Na+/K+ pump currents.
• Intracellular calcium concentration ([Ca2+]i) was monitored using Fura-2/AM.
• Cells were exposed to varying concentrations of extracellular K+, intracellular Na+, and dihydroouabain.

Main Results:

• Na+/K+ pump currents were identified and characterized, showing sensitivity to dihydroouabain with a half-maximal inhibitory concentration of 21 µmol/l.
• Pump currents were enhanced by increased intracellular Na+ concentration, with half-maximal activation around 60 mmol/l.
• The nystatin-perforated-patch method yielded pump currents approximately four times larger than the conventional whole-cell technique.

Conclusions:

• The Na+/K+ pump in human umbilical cord vein endothelial cells exhibits distinct kinetic properties, including a higher sensitivity to dihydroouabain compared to other tissues.
• Intracellular sodium and extracellular potassium are key regulators of Na+/K+ pump activity in these cells.
• The choice of patch-clamp technique significantly impacts the measurement of Na+/K+ pump currents.