Hydrogen ion currents in rat alveolar epithelial cells

Area of Science:

• Cellular Physiology
• Respiratory Biology
• Ion Transport Mechanisms

Background:

• Alveolar epithelial cells form the primary barrier in the lung's gas exchange region.
• Understanding ion transport in these cells is crucial for lung function and disease.
• Previous studies identified voltage-activated currents in other excitable and non-excitable cells.

Purpose of the Study:

• To investigate the presence and characteristics of voltage-activated hydrogen (H+) currents in primary cultured rat alveolar epithelial cells.
• To determine the properties of these currents, including activation, deactivation, and modulation by specific ions and buffer conditions.

Main Methods:

• Primary culture of rat alveolar epithelial cells.
• Whole-cell patch-clamp electrophysiology to record ionic currents.
• Ionic substitution to isolate hydrogen currents.
• Manipulation of external pH and pipette buffer concentration.

Main Results:

• Large, voltage-activated, hydrogen-selective currents were observed in alveolar epithelial cells.
• These currents exhibited properties similar to H+ currents in other tissues, including activation by depolarization and inhibition by Cd2+ and Zn2+.
• Current activation kinetics were slower and often sigmoid compared to other cell types.
• Current amplitude was limited by buffer capacity, indicating diffusion limitation at low buffer concentrations.

Conclusions:

• Mammalian alveolar epithelial cells possess voltage-dependent hydrogen currents.
• These currents may play a role in cellular pH regulation and ion homeostasis within the lung epithelium.
• The findings highlight a novel electrophysiological characteristic of alveolar epithelial cells with potential implications for respiratory physiology.