Chen G, Cheung D W
University of Ottawa Heart Institute, Canada.
Eur J Pharmacol. 1992 Nov 13;223(1):33-8. doi: 10.1016/0014-2999(92)90815-l.
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.
用微电极从豚鼠冠状动脉完整内皮制剂记录了内皮细胞对咖啡因和乙酰胆碱（ACh）的膜电位变化。咖啡因以浓度依赖的方式诱导膜的短暂超极化。去除浴液中的Ca2+和用ryanodine（20μM）可抑制这种超极化。它不受3,4,5-三甲氧基苯甲酸8-（二乙氨基）辛酯盐酸盐（TMB-8，10μM）或新霉素（5mM）的影响。ACh诱导内皮细胞持续超极化。在对咖啡因反应无显著影响的浓度下，TMB-8和新霉素抑制ACh诱导的超极化。Ryanodine不抑制对ACh的反应。咖啡因也以浓度依赖的方式抑制ACh诱导的超极化。本研究结果表明，咖啡因和ACh诱导的超极化由不同的Ca2+池介导。
