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Changes in intracellular pH affect calcium currents in Paramecium caudatum
Proceedings of the Royal Society of London. Series B, Biological Sciences
|September 22, 1982
Summary
Intracellular pH directly influences membrane excitability in Paramecium. Changes in internal pH affect calcium currents, altering electrical activity and action potential generation.
Area of Science:
- Cellular physiology
- Ion channel function
Background:
- Membrane excitability is crucial for cellular function.
- The role of intracellular pH (pHi) in regulating ion channels is not fully understood.
Purpose of the Study:
- To investigate the relationship between intracellular pH and membrane excitability in Paramecium caudatum.
- To determine how alterations in pHi affect calcium currents and action potential generation.
Main Methods:
- Intracellular pH measurement using ion-sensitive microelectrodes.
- Electrical properties assessed via current stimulation and two-electrode voltage clamp.
- Calcium currents modulated by altering intracellular pH.
Main Results:
- Resting pHi in Paramecium is approximately 6.80.
- Intracellular alkalinization enhanced early calcium current; acidification depressed it.
- Alkalinization converted graded calcium responses to all-or-none action potentials.
Conclusions:
- Intracellular pH directly modulates calcium channel activity in Paramecium.
- pHi plays a critical role in regulating membrane excitability and action potential dynamics.
- A model suggests intracellular protonation blocks calcium channel permeability.