Depolarization modulates endothelial cell calcium influx and microvessel permeability

Area of Science:

• Physiology
• Cell Biology
• Biophysics

Background:

• Microvessel permeability is crucial for tissue homeostasis.
• Calcium ionophores disrupt microvessel barrier function.
• The role of membrane potential in regulating microvessel permeability is not fully understood.

Purpose of the Study:

• To investigate how high-potassium solutions attenuate calcium ionophore-induced increases in microvessel permeability.
• To determine the influence of membrane potential on cytoplasmic calcium concentration ([Ca2+]i) and hydraulic conductivity (Lp) in microvessels.

Main Methods:

• Single perfused microvessels were used to measure [Ca2+]i and Lp.
• Experiments involved exposure to calcium ionophores (ionomycin, A23187) in normal and high-potassium Ringer solutions.
• Membrane potential was assessed using the dye bisoxonol.

Main Results:

• High-potassium solutions significantly reduced the ionophore-induced increase in [Ca2+]i and Lp compared to normal Ringer solution.
• Increasing extracellular calcium in high-potassium solution restored the peak [Ca2+]i.
• The observed changes in [Ca2+]i and Lp were abolished in calcium-free solutions.

Conclusions:

• High-potassium solutions attenuate microvessel hyperpermeability by reducing the rise in cytoplasmic calcium.
• Results support the hypothesis that microvessel permeability is modulated by the membrane potential of endothelial cells and/or pericytes.