pH effects on basolateral membrane ion conductances in gallbladder epithelium

Area of Science:

• Cellular physiology
• Electrophysiology
• Epithelial transport

Background:

• The basolateral membrane voltage of epithelial cells is crucial for transport processes.
• Understanding the factors influencing membrane voltage, such as pH, is essential for comprehending cell function.

Purpose of the Study:

• To investigate the pH sensitivity of the basolateral membrane voltage in Necturus gallbladder epithelial cells.
• To determine whether changes in intracellular pH (pHi) or extracellular pH (pHo) are responsible for observed voltage alterations.
• To elucidate the ionic mechanisms underlying pH-induced changes in membrane potential.

Main Methods:

• Utilized conventional and pH-sensitive intracellular microelectrodes to measure basolateral membrane voltage (Vcs) and pHi.
• Manipulated extracellular CO2 and HCO3- concentrations to alter pHo and pHi.
• Assessed changes in Vcs and pHi under varying ionic conditions (K+, Cl-).

Main Results:

• Elevating CO2 caused depolarization of Vcs and decreased pHi, but depolarization was linked to extracellular pH changes.
• Changes in extracellular pH significantly altered Vcs, while intracellular pH changes had minimal effect.
• Reduced extracellular HCO3- (1 mM) altered Vcs responses to K+ and Cl- challenges, suggesting changes in ion permeability.

Conclusions:

• Basolateral membrane voltage of Necturus gallbladder epithelial cells is sensitive to extracellular pH, not intracellular pH.
• Observed voltage changes are likely due to a decrease in basolateral K+ permeability and an increase in Cl- permeability.
• These findings provide insights into the regulation of epithelial cell membrane potential by pH and ion transport.