title: Potentiation of acetylcholine-induced responses in freshly isolated rabbit aortic endothelial cells.
abstract: Acetylcholine (ACh)-induced membrane hyperpolarization was studied in freshly isolated endothelial cells from rabbit aorta. Ten microM ACh induced transient hyperpolarization due to the opening of Ca(2+)-sensitive K+ channels, sensitive to TEA and charybdotoxin (CTX). The membrane potential response was accompanied by an increase in intracellular Ca2+ [Ca2+]i. Pretreatment of endothelial cells with 20 microM ATP, 0.2 microM bradykinin or 0.1 microM platelet-aggregating factor, which induced either a transient hyperpolarization or no response, changed the subsequent ACh-induced response to a large maintained hyperpolarization. This sustained membrane hyperpolarization was also due to the opening of Ca(2+)-activated K+ channels as confirmed by CTX and TEA blockade, and was related to elevated [Ca2+]i measured by fura-2 fluorescence. Pertussis toxin blocked potentiation, indicating involvement of a G protein. The linkage to receptor-operated Ca2+ (ROC)-entry was suggested by observations that the maintained hyperpolarization during potentiation was dependent on extracellular Ca2+ and was abolished by the ROC blockers SKF-96365 and Ni2+. Inhibition of the Ca2+ pump of the endoplasmic reticulum mimicked the potentiating effect of the agonists. The results suggest that crosstalk between the agonists in endothelial cells involves Ca2+ movements and that this crosstalk is important for the generation of endothelial secretions.
authors.affiliation: Department of Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada.
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: W
authors.initials: W
authors.lastname: Chu
authors.forename: C
authors.initials: C
authors.lastname: van Breemen
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic; D001779:Blood Coagulation Factors / Q000494:pharmacology; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002413:Cations, Divalent / Q000378:metabolism; D018999:Charybdotoxin / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology; D006873:Hydroquinones / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007424:Intracellular Fluid / Q000378:metabolism; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008564:Membrane Potentials / Q000187:drug effects; D009532:Nickel / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D018408:Patch-Clamp Techniques; D037342:Pertussis Toxin; D010972:Platelet Activating Factor; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated; D011817:Rabbits; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D001779:Blood Coagulation Factors; D002121:Calcium Channel Blockers; D002413:Cations, Divalent; D004791:Enzyme Inhibitors; D006873:Hydroquinones; D007093:Imidazoles; D007211:Indoles; D051036:Large-Conductance Calcium-Activated Potassium Channels; D010972:Platelet Activating Factor; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D013757:Tetraethylammonium Compounds; D010566:Virulence Factors, Bordetella; C087375:charybdotoxin receptor; D018999:Charybdotoxin; D009569:Nitric Oxide; D019789:Tetraethylammonium; D019284:Thapsigargin; D009532:Nickel; D000255:Adenosine Triphosphate; C018855:2-tert-butylhydroquinone; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000252:Calcium-Transporting ATPases; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D000109:Acetylcholine; D001920:Bradykinin; D002118:Calcium; C000543:cyclopiazonic acid