Background The rapidly activating delayed rectifier potassium current （/Kr）, whose pore-forming alpha subunit is encoded by the human ether-a-go-go-related gene （hERG）, is a key contributor to the third phase of a...Background The rapidly activating delayed rectifier potassium current （/Kr）, whose pore-forming alpha subunit is encoded by the human ether-a-go-go-related gene （hERG）, is a key contributor to the third phase of action potential repolarization. The aim of this study was to investigate the effect and mechanism of arecoline hydrobromide induced inhibition of hERG K^＋ current （/hERG）. Methods Transient transfection of hERG channel cDNA plasmid pcDNA3.1 into the cultured HEK293 cells was performed using Lipofectamine. A standard whole-cell patch-clamp technique was used to record the /hI=RG before and after the exposure to arecoline. Results Arecoline decreased the amplitude and the density of the /bERG in a concentration-dependent manner （IC5o=9.55 μmol/L）. At test potential of ＋60 mV, the magnitude of lhERG tail at test pulse of -40 mV was reduced from （151.7±6.2） pA/pF to （84.4±7.6） pA/pF （P 〈0.01, n=20） and the magnitude of IhERG tail at test pulse of -110 mV was reduced from （-187.5±9.8） pA/pF to （-97.6±12.6） pA/pF （P 〈0.01, n=20）. The blockade of arecoline in the open and inactivated state was significant in a state-dependent manner. The maximal blockade was achieved in the inactivated state. Studies of gating mechanism showed that the steady-state activation curve of IhERG was significantly negatively shifted by arecoline. Time constants of activation were shortened. Steady-state inactivation curve and time constants of fast inactivation were not significantly affected by arecoline. Furthermore, the inhibition of IhERG by arecoline was characterized markedly by a frequency-dependent manner from 0.03 to 1.00 Hz pulse. Conclusion Arecoline could potently block IhERG in both frequency and state-dependent manner.展开更多
基金This study was supported by the grants from the National Natural Science Foundation of China （No. 81170177 and No. 30770901 ）.Acknowledgment： We would like to thank Prof. Priori, University of Pavia in Italy for generously providing the hERG plasmid.
文摘Background The rapidly activating delayed rectifier potassium current （/Kr）, whose pore-forming alpha subunit is encoded by the human ether-a-go-go-related gene （hERG）, is a key contributor to the third phase of action potential repolarization. The aim of this study was to investigate the effect and mechanism of arecoline hydrobromide induced inhibition of hERG K^＋ current （/hERG）. Methods Transient transfection of hERG channel cDNA plasmid pcDNA3.1 into the cultured HEK293 cells was performed using Lipofectamine. A standard whole-cell patch-clamp technique was used to record the /hI=RG before and after the exposure to arecoline. Results Arecoline decreased the amplitude and the density of the /bERG in a concentration-dependent manner （IC5o=9.55 μmol/L）. At test potential of ＋60 mV, the magnitude of lhERG tail at test pulse of -40 mV was reduced from （151.7±6.2） pA/pF to （84.4±7.6） pA/pF （P 〈0.01, n=20） and the magnitude of IhERG tail at test pulse of -110 mV was reduced from （-187.5±9.8） pA/pF to （-97.6±12.6） pA/pF （P 〈0.01, n=20）. The blockade of arecoline in the open and inactivated state was significant in a state-dependent manner. The maximal blockade was achieved in the inactivated state. Studies of gating mechanism showed that the steady-state activation curve of IhERG was significantly negatively shifted by arecoline. Time constants of activation were shortened. Steady-state inactivation curve and time constants of fast inactivation were not significantly affected by arecoline. Furthermore, the inhibition of IhERG by arecoline was characterized markedly by a frequency-dependent manner from 0.03 to 1.00 Hz pulse. Conclusion Arecoline could potently block IhERG in both frequency and state-dependent manner.
