Direct current electrical measurement in epithelia: steady-state and transient analysis

Area of Science:

• Physiology
• Biophysics
• Electrophysiology

Background:

• Determining biological tissue resistance is crucial for understanding cellular function.
• Previous methods may not accurately account for complex cellular responses like polarization.
• Gastric mucosa exhibits unique electrical properties relevant to acid secretion.

Purpose of the Study:

• To present a refined method for measuring biological tissue resistance using potential difference (PD) responses to step currents.
• To differentiate between true resistance and polarization artifacts in biological tissues, specifically gastric mucosa.
• To elucidate the mechanisms of ion transport and cellular pathways involved in gastric acid secretion.

Main Methods:

• Measurement of potential difference (PD) changes in response to applied step currents.
• Calculation of tissue resistance by dividing the change in PD by the applied current after dielectric capacitor charging.
• Analysis of PD responses in gastric mucosa to identify and exclude polarization-induced voltage changes.
• Correlating resistance measurements with acid secretion rates and ion flux.

Main Results:

• A method was developed to determine tissue resistance by analyzing PD changes after dielectric capacitor charging.
• In gastric mucosa, a portion of the PD increase after capacitor charging is due to EMF polarization and should be excluded for accurate resistance measurement.
• Resistance measurements demonstrated a neutral mechanism for HCO3- efflux and Cl- influx into oxyntic cells during acid secretion.
• Transmucosal resistance was found to be inversely proportional to the rate of acid secretion.
• The low resistance of secreting frog fundus is attributed to the lumen-tubular cell pathway, while parallel pathways (paracellular and surface cell) exhibit high resistance.

Conclusions:

• The developed method allows for accurate determination of biological tissue resistance by accounting for polarization effects.
• Resistance measurements provide evidence for specific ion transport mechanisms in gastric oxyntic cells during acid secretion.
• Understanding the electrical resistance of different cellular pathways is key to comprehending gastric acid secretion regulation.
• Further analysis of resistance and PD measurements aids in understanding the electrogenic or neutral nature of the proton pump in intact tissues.