Frequency- and state-dependent blockade of human ether-a-go-go-related gene K+ channel by arecoline hydrobromide.
- Author:
Xu-yan ZHAO
1
;
Yu-qi LIU
;
Yi-cheng FU
;
Bin XU
;
Jin-liao GAO
;
Xiao-qin ZHENG
;
Min LIN
;
Mei-yan CHEN
;
Yang LI
Author Information
- Publication Type:Journal Article
- MeSH: Action Potentials; drug effects; Arecoline; pharmacology; Dose-Response Relationship, Drug; ERG1 Potassium Channel; Ether-A-Go-Go Potassium Channels; antagonists & inhibitors; physiology; HEK293 Cells; Humans
- From: Chinese Medical Journal 2012;125(6):1068-1075
- CountryChina
- Language:English
-
Abstract:
BACKGROUNDThe rapidly activating delayed rectifier potassium current (I(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 (I(hERG)).
METHODSTransient 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 I(hERG) before and after the exposure to arecoline.
RESULTSArecoline decreased the amplitude and the density of the I(hERG) in a concentration-dependent manner (IC(50) = 9.55 mmol/L). At test potential of +60 mV, the magnitude of I(hERG) 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 I(hERG) 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 I(hERG) 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 I(hERG) by arecoline was characterized markedly by a frequency-dependent manner from 0.03 to 1.00 Hz pulse.
CONCLUSIONArecoline could potently block I(hERG) in both frequency and state-dependent manner.