Acetylcholine induces Ca-dependent K currents in rabbit endothelial cells

Area of Science:

• Cardiovascular Biology
• Cell Physiology
• Pharmacology

Background:

• Endothelial cells in the rabbit aorta play a crucial role in vascular function.
• Acetylcholine (ACh) is a key neurotransmitter with diverse effects on cardiovascular tissues.

Purpose of the Study:

• To investigate the effects of acetylcholine (ACh) on endothelial cell membrane potential and current.
• To elucidate the specific receptor subtypes and intracellular mechanisms involved in ACh-mediated responses in rabbit aorta endothelial cells.

Main Methods:

• Patch-clamp technique (whole-cell voltage-clamp and single-channel recording) was employed.
• Electrophysiological recordings were performed on dispersed endothelial cells from rabbit aorta.
• Pharmacological agents including atropine, pirenzepine, AF-DX 116, caffeine, ryanodine, heparin, and methylene blue were used to probe the mechanisms.

Main Results:

• ACh induced membrane hyperpolarization and an outward current in endothelial cells.
• The ACh-induced outward current was blocked by atropine, indicating muscarinic receptor involvement.
• Pirenzepine and AF-DX 116 partially inhibited the current, suggesting the presence of both M1 and M2 receptor subtypes.
• Caffeine, ryanodine, and heparin reduced the current amplitude, implicating intracellular calcium release.
• Single-channel recordings identified a Ca-dependent K-channel (9 pS conductance) opened by ACh.
• Methylene blue inhibited the outward current from the extracellular side.

Conclusions:

• Endothelial cells of the rabbit aorta express both M1 and M2 muscarinic receptor subtypes.
• ACh activates a Ca-dependent K channel in these cells, mediated by the release of intracellular calcium.
• These findings provide insights into the electrophysiological effects of ACh on aortic endothelial cells and the underlying signaling pathways.