Background Shensong Yangxin （SSYX） is one of the compound recipe of Chinese materia medica. This study was conducted to investigate the effects of SSYX on sodium current （/Na）, L-type calcium current （/Ca.L）, tr...Background Shensong Yangxin （SSYX） is one of the compound recipe of Chinese materia medica. This study was conducted to investigate the effects of SSYX on sodium current （/Na）, L-type calcium current （/Ca.L）, transient outward potassium current （/to）, delayed rectifier current （/K）, and inward rectifier potassium currents （/K1） in isolated ventricular myocytes. Methods Whole cell patch-clamp technique was used to study ion channel currents in enzymatically isolated guinea pig or rat ventricular myocytes. Results SSYX decreased peak Na by （44.84±7.65）% from 27.21±5.35 to 14.88±2..75 pA/pF （n=-5, P〈0.05）. The medicine significantly inhibited the /Ca,L. At concentrations of 0.25, 0.50, and 1.00 g/100 ml, the peak/Ca,L was reduced by （19.22±1.10）%, （44.82±6.50）% and （50.69±5.64）%, respectively （n=5, all P〈0.05）. SSYX lifted the I-V curve of both /Na and /Ca,L without changing the threshold, peak and reversal potentials. At the concentration of 0.5%, the drug blocked the transient component of /to by 50.60% at membrane voltage of 60 mV and negatively shifted the inactive curve and delayed the recovery from channel inactivation. The tail current density of /K was decreased by （30.77±1.11）% （n=5, P〈0.05） at membrane voltage of 50 mV after exposure to the medicine and the time-dependent activity of /K was also inhibited. Similar to the effect on /K, the SSYX inhibited /K1 by 33.10% at the test potential of -100 mV with little effect on reversal potential and the rectification property. Conclusions The experiments revealed that SSYX could block multiple ion channels such as /Na /Ca,L, /k, /to and /K1, which may change the action potential duration and contribute to some of its antiarrhythmic effects.展开更多
Background Atrial fibrillation is a common arrhythmia with multi-factorial pathogenesis. Recently, a single nucleotide polymorphism （G/T） at position 1057 in the KCNE4 gene, resulting in a glutamic acid （Glu, E）/a...Background Atrial fibrillation is a common arrhythmia with multi-factorial pathogenesis. Recently, a single nucleotide polymorphism （G/T） at position 1057 in the KCNE4 gene, resulting in a glutamic acid （Glu, E）/aspartic acid （Asp, D） substitution at position 145 of the KCNE4 peptide, was found in our laboratory to be associated with idiopathic atrial fibrillation （atrial fibrillation more frequent with KCNE4 145D）. However, the functional effect of the KCNE4 145E/D polymorphism is still unknown. Methods We constructed KCNE4 （145E/D） expression plasmids and transiently co-transfected them with the KCNQ1 gene into Chinese hamster ovary-K1 cells and performed whole-cell patch-clamping recording to identify the possible functional consequences of the single nucleotide polymorphism. Quantitative data were analyzed by Student＇s t test. Probability values less than 0.05 were considered statistically significant. Results A slowly activating, non-inactivating voltage-dependent current （（24.0±2.9） pA/pF, at ＋60 mV）） could be recorded in the cells transfected with KCNQ1 alone. Co-expression of wild type KCNE4 inhibited the KCNQ1 current （（7.3± 1.1 ） pA/pF））. By contrast, co-expression of KCNE4 （145D） augment the KCNQ 1 current （（42.9 ±3.7） pA/pF））. The V1/2 of activation for the KCNQI/KCNE4 （145D） current was shifted significantly towards the depolarizing potential compared to that for the KCNQ1 current （（-2.3±0.2） mv vs （-13.0±1.5） mv, P 〈 0.01）） without changing the slope factorK. Furthermore, KCNE4 （145D） also affected the activation and deactivation kinetics of KCNQ1 channels. Conclusion We provide experimental evidence that the KCNE4 （145E/D） polymorphism exerts the effect of ＂gain of function＂ on the KCNQ1 channel. It may underlie the genetic mechanism of atrial fibrillation. Further studies on the functional association between IKs and KCNE4 （145D） polymorphism in cardiac myocytes are suggested.展开更多
文摘Background Shensong Yangxin （SSYX） is one of the compound recipe of Chinese materia medica. This study was conducted to investigate the effects of SSYX on sodium current （/Na）, L-type calcium current （/Ca.L）, transient outward potassium current （/to）, delayed rectifier current （/K）, and inward rectifier potassium currents （/K1） in isolated ventricular myocytes. Methods Whole cell patch-clamp technique was used to study ion channel currents in enzymatically isolated guinea pig or rat ventricular myocytes. Results SSYX decreased peak Na by （44.84±7.65）% from 27.21±5.35 to 14.88±2..75 pA/pF （n=-5, P〈0.05）. The medicine significantly inhibited the /Ca,L. At concentrations of 0.25, 0.50, and 1.00 g/100 ml, the peak/Ca,L was reduced by （19.22±1.10）%, （44.82±6.50）% and （50.69±5.64）%, respectively （n=5, all P〈0.05）. SSYX lifted the I-V curve of both /Na and /Ca,L without changing the threshold, peak and reversal potentials. At the concentration of 0.5%, the drug blocked the transient component of /to by 50.60% at membrane voltage of 60 mV and negatively shifted the inactive curve and delayed the recovery from channel inactivation. The tail current density of /K was decreased by （30.77±1.11）% （n=5, P〈0.05） at membrane voltage of 50 mV after exposure to the medicine and the time-dependent activity of /K was also inhibited. Similar to the effect on /K, the SSYX inhibited /K1 by 33.10% at the test potential of -100 mV with little effect on reversal potential and the rectification property. Conclusions The experiments revealed that SSYX could block multiple ion channels such as /Na /Ca,L, /k, /to and /K1, which may change the action potential duration and contribute to some of its antiarrhythmic effects.
文摘Background Atrial fibrillation is a common arrhythmia with multi-factorial pathogenesis. Recently, a single nucleotide polymorphism （G/T） at position 1057 in the KCNE4 gene, resulting in a glutamic acid （Glu, E）/aspartic acid （Asp, D） substitution at position 145 of the KCNE4 peptide, was found in our laboratory to be associated with idiopathic atrial fibrillation （atrial fibrillation more frequent with KCNE4 145D）. However, the functional effect of the KCNE4 145E/D polymorphism is still unknown. Methods We constructed KCNE4 （145E/D） expression plasmids and transiently co-transfected them with the KCNQ1 gene into Chinese hamster ovary-K1 cells and performed whole-cell patch-clamping recording to identify the possible functional consequences of the single nucleotide polymorphism. Quantitative data were analyzed by Student＇s t test. Probability values less than 0.05 were considered statistically significant. Results A slowly activating, non-inactivating voltage-dependent current （（24.0±2.9） pA/pF, at ＋60 mV）） could be recorded in the cells transfected with KCNQ1 alone. Co-expression of wild type KCNE4 inhibited the KCNQ1 current （（7.3± 1.1 ） pA/pF））. By contrast, co-expression of KCNE4 （145D） augment the KCNQ 1 current （（42.9 ±3.7） pA/pF））. The V1/2 of activation for the KCNQI/KCNE4 （145D） current was shifted significantly towards the depolarizing potential compared to that for the KCNQ1 current （（-2.3±0.2） mv vs （-13.0±1.5） mv, P 〈 0.01）） without changing the slope factorK. Furthermore, KCNE4 （145D） also affected the activation and deactivation kinetics of KCNQ1 channels. Conclusion We provide experimental evidence that the KCNE4 （145E/D） polymorphism exerts the effect of ＂gain of function＂ on the KCNQ1 channel. It may underlie the genetic mechanism of atrial fibrillation. Further studies on the functional association between IKs and KCNE4 （145D） polymorphism in cardiac myocytes are suggested.
