Acetylcholine induces Ca-dependent K currents in rabbit endothelial cells.
Effects of acetylcholine (ACh) on the membrane potential and current recorded from endothelial cells dispersed from the rabbit aorta were investigated using the patch-clamp technique. ACh hyperpolarized the endothelial cell membrane. Using the whole-cell voltage-clamp procedure, ACh (10(-6) M) induced an outward current, and this current was blocked by atropine (10(-6) M). Application of either pirenzepine (3 x 10(-7) M) or AF-DX 116 (3 x 10(-6) M) slightly inhibited the ACh-induced outward current, and simultaneous application of these two blockers markedly inhibited the outward current. Application of caffeine (2 x 10(-2) M), ryanodine (10(-5) M) or heparin (10(-5) g/ml) reduced the amplitude of the ACh-induced outward current. A single-channel current recording using the patch-clamp technique revealed that ACh opens a Ca-dependent K-channel with a single-channel current conductance of 9 pS. These results indicate that both M1 and M2 receptor subtypes are present in endothelial cells of the rabbit aorta and that ACh activates the Ca-dependent K channel via release of Ca from intracellular store sites. In addition, methylene blue inhibited the ACh-induced outward current from the outside membrane.
Sakai
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Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan.
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology / Q000187:drug effects; D002118:Calcium / Q000502:physiology*; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008751:Methylene Blue / Q000494:pharmacology; D010276:Parasympatholytics / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects*; D011817:Rabbits
D010276:Parasympatholytics; D015221:Potassium Channels; D000109:Acetylcholine; D002118:Calcium; D008751:Methylene Blue