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Tetrodotoxin-sensitive sodium current in sheep lymphatic smooth muscle
M A Hollywood1, K D Cotton, K D Thornbury
1Department of Physiology, School of Biomedical Science, Queen's University of Belfast, UK.
The Journal of Physiology
|August 15, 1997
Summary
Sheep lymphatic smooth muscle cells possess fast inward sodium currents (TTX-sensitive) crucial for action potential generation and vessel contraction. These currents are essential for lymphatic muscle function and spontaneous contractions.
Area of Science:
- Physiology
- Ion Channels
- Smooth Muscle Biology
Background:
- Lymphatic smooth muscle cells generate electrical activity essential for lymph transport.
- Understanding the ion channels involved in lymphatic smooth muscle excitability is critical.
Purpose of the Study:
- To investigate the properties of fast inward currents in sheep lymphatic smooth muscle cells.
- To determine the role of these currents in action potential generation and lymphatic vessel contraction.
Main Methods:
- Whole-cell patch-clamp electrophysiology on isolated sheep lymphatic smooth muscle cells.
- Voltage-clamp and current-clamp recordings.
- Pharmacological assessment using tetrodotoxin (TTX).
Main Results:
- Depolarization elicited fast inward currents activated positive to -40 mV, peaking at 0 mV.
- These currents were abolished by replacing NaCl with choline chloride, indicating sodium dependence.
- The currents were highly sensitive to tetrodotoxin (TTX), with half-maximal inhibition at 17 nM.
- Action potentials with rapid upstrokes were recorded and blocked by TTX.
- Spontaneous contractions of lymphatic vessels were inhibited by TTX.
Conclusions:
- Sheep lymphatic smooth muscle cells express TTX-sensitive sodium channels responsible for inward currents.
- These sodium currents play a significant role in the generation of action potentials and spontaneous contractions in lymphatic vessels.