Pharmacological distinction of the hyperpolarization response to caffeine and acetylcholine in guinea-pig coronary endothelial cells.
Membrane potential changes in endothelial cells in response to caffeine and acetylcholine (ACh) were recorded with microelectrodes from an intact endothelium preparation from the guinea-pig coronary artery. Caffeine induced a transient hyperpolarization of the membrane in a concentration-dependent manner. The hyperpolarization was inhibited by removal of Ca2+ from the bathing medium and by ryanodine (20 microM). It was not affected by 3,4,5-trimethoxybenzoic acid 8-(diethylamino) octyl ester hydrochloride (TMB-8, 10 microM) or neomycin (5 mM). ACh induced a sustained hyperpolarization in endothelial cells. At concentrations that caused no significant effects on the caffeine response, TMB-8 and neomycin inhibited hyperpolarization induced by ACh. Ryanodine did not inhibit the response to ACh. The ACh-induced hyperpolarization was also inhibited by caffeine in a concentration-dependent manner. Results from the present study suggest that hyperpolarizations induced by caffeine and ACh are mediated by separate Ca2+ pools.
Chen
G
G
University of Ottawa Heart Institute, Canada.
Cheung
D W
DW
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000187:drug effects*; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007293:Inosine Triphosphate / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009355:Neomycin / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology
D002121:Calcium Channel Blockers; D007293:Inosine Triphosphate; D012433:Ryanodine; D002110:Caffeine; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D009355:Neomycin; D000109:Acetylcholine; D002118:Calcium