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Outward currents in smooth muscle cells isolated from sheep mesenteric lymphatics
K D Cotton1, M A Hollywood, N G McHale
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 calcium-activated potassium channels and multiple voltage-dependent outward currents. These ion channel activities are crucial for lymphatic smooth muscle function and regulation.
Area of Science:
- Physiology
- Ion Channel Biology
- Smooth Muscle Research
Background:
- Lymphatic smooth muscle cells play a vital role in lymph transport.
- Understanding the ion channel mechanisms governing lymphatic smooth muscle contractility is essential.
Purpose of the Study:
- To characterize the membrane currents in isolated sheep mesenteric lymphatic smooth muscle cells.
- To identify the types of ion channels responsible for these currents.
Main Methods:
- Patch-clamp technique (whole-cell and single-channel recordings) on isolated smooth muscle cells.
- Application of pharmacological agents (Nifedipine, Bay K 8644, iberiotoxin, penitrem A, TEA, 4-AP) to modulate channel activity.
- Analysis of Ca(2+)-activated and voltage-dependent currents.
Main Results:
- Identified large conductance, Ca(2+)- and voltage-sensitive K+ channels mediating outward currents.
- Demonstrated a voltage-dependent outward current with inactivation, partially blocked by TEA and 4-AP, suggesting multiple components.
- Showed that Ca(2+)-activated currents were significantly reduced by iberiotoxin.
Conclusions:
- Sheep lymphatic smooth muscle cells possess a Ca(2+)-activated current, primarily via large conductance Ca(2+)-activated K+ channels.
- Multiple components of voltage-dependent outward currents, similar to delayed rectifier currents, are present in these cells.
- These ion channel currents are critical for the electrical activity and function of lymphatic smooth muscle.