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Ca(2+)-activated Cl(-) current in sheep lymphatic smooth muscle.
H M Toland1, K D McCloskey, K D Thornbury
1Smooth Muscle Group, Department of Physiology, Queen's University, Belfast BT9 7BL, United Kingdom.
American Journal of Physiology. Cell Physiology
|October 13, 2000
Summary
A calcium-activated chloride current (I(Cl(Ca))) is crucial for spontaneous lymphatic smooth muscle activity. This chloride current influences electrical activity and fluid output in sheep lymphatics.
Area of Science:
- Physiology
- Ion Channels
- Smooth Muscle Biology
Background:
- Sheep mesenteric lymphatic smooth muscle cells exhibit complex electrical activity.
- Understanding the ion channels involved is key to comprehending lymphatic function.
Purpose of the Study:
- To investigate the role of chloride currents in sheep mesenteric lymphatic smooth muscle.
- To characterize the properties of a slowly developing current and its contribution to electrical activity.
Main Methods:
- Perforated patch-clamp technique on sheep mesenteric lymphatic smooth muscle cells.
- Voltage-clamp and current-clamp recordings.
- Pharmacological manipulation with nifedipine, BAY K 8644, and anthracene-9-carboxylic acid (9-AC).
Main Results:
- A slowly developing current, distinct from L-type Ca(2+) current (I(Ca(L))), was identified.
- This slow current was sensitive to chloride concentrations and blocked by 9-AC.
- 9-AC also inhibited spontaneous transient depolarizations, action potentials, and reduced lymphatic fluid output.
Conclusions:
- A calcium-activated chloride current (I(Cl(Ca))) plays a significant role in the electrical activity of sheep mesenteric lymphatics.
- This chloride current is essential for spontaneous contractions and fluid pumping in lymphatic vessels.