Calcium waves induced by large voltage pulses in fish keratocytes

Area of Science:

• Cell Biology
• Biophysics

Background:

• Intracellular calcium (Ca2+) waves play critical roles in cellular processes.
• Understanding the mechanisms that initiate and propagate these waves is essential.

Purpose of the Study:

• To investigate the induction and characteristics of intracellular calcium waves in fish keratocytes using electric field pulses.
• To elucidate the role of membrane potential, calcium influx, and intracellular calcium release in wave generation.

Main Methods:

• Fish keratocytes were subjected to electric field pulses (55-120 V/cm).
• Intracellular calcium concentrations were monitored using two-photon excited fluorescence microscopy and the indo-1 indicator.
• The effects of varying electric field strengths, calcium concentrations, and calcium channel blockers were assessed.

Main Results:

• Electric field pulses reliably induced intracellular calcium waves, primarily initiating at the hyperpolarized side of the cell.
• Wave generation was dependent on the voltage drop across the cell membrane, with significant induction above 150 mV and saturation above 300 mV.
• Waves required extracellular calcium influx and release from intracellular stores, as indicated by blockage with cobalt chloride and verapamil, and inhibition by thapsigargin.

Conclusions:

• Electric field pulses can effectively stimulate Ca2+ influx through plasma membrane channels, initiating intracellular calcium waves.
• A threshold intracellular Ca2+ concentration triggers the release of Ca2+ from intracellular stores, leading to wave propagation.
• The observed wave dynamics (velocity ~66 µm/s, rise time ~68 ms) support a wave amplification model involving effective diffusivity (D ~300 µm²/s).