Apical and basolateral membrane conductances in the TBM cell line

Area of Science:

• Cellular Physiology
• Epithelial Transport
• Electrophysiology

Background:

• Cultured cell lines offer advantages over whole organs for studying epithelial transport.
• Existing methods may not fully capture the complex physiological environment of epithelia.
• Need for advanced techniques to investigate ionic conductances in cultured epithelial models.

Purpose of the Study:

• To develop and apply a novel technique for simultaneous intracellular and transepithelial electrophysiological measurements.
• To characterize the electrophysiological properties of the TBM 18/23 (toad bladder origin) cell line.
• To investigate the regulation of membrane ionic conductances in a cultured tight epithelium model.

Main Methods:

• Development of a technique for simultaneous intracellular and transepithelial electrophysiological measurements.
• Culturing of the TBM 18/23 cell line on thin collagen membranes.
• Application of circuit analysis and pharmacological agents (amiloride, barium) to assess membrane conductances.

Main Results:

• Established transepithelial and basolateral membrane potentials (-30 +/- 11 mV and -72 +/- 8 mV, respectively).
• Estimated apical and basolateral membrane conductances (0.7 +/- 0.1 mS/cm2 and 2.8 +/- 0.4 mS/cm2, respectively).
• Identified a sodium-selective apical pathway and a barium-sensitive, potassium-selective basolateral pathway, with basolateral conductance sensitive to long-term sodium transport inhibition.

Conclusions:

• The developed technique enables detailed electrophysiological analysis of cultured epithelia.
• The TBM 18/23 cell line serves as a valuable model for studying epithelial ion transport.
• Demonstrated regulation of basolateral membrane conductance in response to changes in sodium transport.