Membrane potential measurement in parotid acinar cells

Area of Science:

• Physiology
• Cell Biology
• Membrane Transport

Background:

• Acinar cells in salivary glands play a crucial role in secretion.
• Understanding their membrane potential is key to comprehending gland function.
• Previous studies had varying reports on salivary acinar cell membrane potential.

Purpose of the Study:

• To investigate the resting membrane potential of mouse parotid acinar cells.
• To determine the influence of neurotransmitters like acetylcholine (ACh) and adrenaline on membrane potential.
• To elucidate the role of extracellular potassium concentration ([K]o) and the Na-K pump in maintaining membrane potential.

Main Methods:

• Intracellular recording of membrane potential in isolated mouse parotid acinar cells.
• Superfusion of cells with various physiological salt solutions, including Krebs-Henseleit solution.
• Manipulation of extracellular ion concentrations, specifically potassium ([K]o) and sodium ([Na]o).
• Application of neurotransmitters (ACh, adrenaline) and inhibitors (atropine, Strophanthin-G).

Main Results:

• The mean resting membrane potential was -68.5 mV.
• Acetylcholine and adrenaline induced a transient hyperpolarization.
• Membrane potential was highly dependent on [K]o, with a tenfold increase causing a 50 mV depolarization.
• K-free solutions induced hyperpolarization, with a pronounced effect after prolonged deprivation, blocked by Strophanthin-G.
• The Na-K pump was found to be electrogenic, especially in sodium-loaded cells.

Conclusions:

• Mouse parotid acinar cell membrane potential magnitude and K-dependence are similar to muscle and nerve cells.
• The Na-K pump is electrogenic in these cells, contributing to membrane potential regulation.
• These findings provide a clearer understanding of salivary acinar cell electrophysiology.