The transmural heterogeneous changes of transient outward potassium currents (Ito) in rabbit hypertrophic cardiaomyocytes and the effects of long-term prophylactic treatment with volsartan were investigated. Rabbits w...The transmural heterogeneous changes of transient outward potassium currents (Ito) in rabbit hypertrophic cardiaomyocytes and the effects of long-term prophylactic treatment with volsartan were investigated. Rabbits were divided into hypertrophy group (left ventricular hypertrophy induced by partial ligation of abdominal aorta), vol-treated group (volsartan was administrated after the ligation), and control group (sham operated). Myocytes were isolated by a two-step enzymatical method. The sub-endocardial (Endo) and sub-epicardium (Epi) tissues were separated from midmyocardium (Mid) with a razor. Whole-cell patch-clamp technique was used to record potassium currents. The results showed that membrane capacitance was larger in hypertrophic cells than those in control and vol-treated cells (P<0.01 vs control cells, n=30). The densities of Ito in hypertrophic cells were reduced by sub-epicardium (Epi) (27.8±2.9) %, midmyocardium (Mid) (41.0±4.7) %, and sub-endocardium (Endo) (20.3±3.4) % compared with those in control cells. The decrease of Ito density was more pronounced in Mid than in Epi and Endo (P<0.01 vs Epi or Endo). There were no significant differences in Ito densities between vol-treated group and control group in three layers separately. In conclusion, volsartan can inhibit the transmural heterogeneous changes of Ito in left ventricular hypertrophic cardiomyocytes in rabbit.展开更多
The electrophysiological properties of potassium ion channels are regarded as a basic index for determining the functional differentiation of neural stem cells. In this study, neural stem cells from the hippocampus of...The electrophysiological properties of potassium ion channels are regarded as a basic index for determining the functional differentiation of neural stem cells. In this study, neural stem cells from the hippocampus of newborn rats were induced to differentiate with neurotrophic growth factor, and the electrophysiological properties of the voltage-gated potassium ion channels were observed. Immunofluorescence staining showed that the rapidly proliferating neural stem cells formed spheres in vitro that expressed high levels of nestin. The differentiated neurons were shown to express neuron-specific enolase. Flow cytometric analysis revealed that the neural stem cells were actively dividing and the percentage of cells in the S ＋ G2/M phase was high. However, the ratio of cells in the S ＋ G2/M phase decreased obviously as differentiation proceeded. Whole-cell patch-clamp re- cordings revealed apparent changes in potassium ion currents as the neurons differentiated. The potassium ion currents consisted of one transient outward potassium ion current and one delayed rectifier potassium ion current, which were blocked by 4-aminopyridine and tetraethylammonium, respectively. The experimental findings indicate that neural stem cells from newborn rat hippo- campus could be cultured and induced to differentiate into functional neurons under defined condi- tions in vitro. The differentiated neurons expressed two types of outward potassium ion cur＇ents similar to those of mature neurons in vivo.展开更多
Acutely isolated mouse hippocampal CA3 pyramidal neurons were exposed to 3 mT static magnetic field,and the characteristics of transient outward K+ channel were studied using the whole-cell patch-clamp technique.The e...Acutely isolated mouse hippocampal CA3 pyramidal neurons were exposed to 3 mT static magnetic field,and the characteristics of transient outward K+ channel were studied using the whole-cell patch-clamp technique.The experiment revealed that the amplitude of transient outward potassium channel current was reduced.The maximum activated current densities of control group and exposure group were 163.62±20.68 pA/pF and 98.74±16.57 pA/pF(n=12,P<0.01) respectively.The static magnetic field exposure affected the activation and inactivation process of transient outward potassium channel current.Due to the magnetic field exposure,the half-activation voltage of the activation curves changed from 5.59±1.96 mV to 27.87±7.24 mV(n=12,P<0.05) ,and the slope factor changed from 19.43±2.11 mV to 25.87±4.22 mV(n=12,P<0.05) .The half-inactivation voltage of the inactivation curves also changed from-56.09±0.89 mV to-57.16±1.10 mV(n=12,P>0.05) and the slope factor of the inactivation curves from 8.69±0.80 mV to 10.87±1.02 mV(n=12,P<0.05) .The results show that the static magnetic field can change the characteristics of transient outward K+ channel,and affect the physiological functions of neurons.展开更多
Background Some studies have confirmed that the right ventricular walls of most rodents, such as canines and humans, have evident transient outward potassium current (I to1) heterogeneity, and this heterogeneity i...Background Some studies have confirmed that the right ventricular walls of most rodents, such as canines and humans, have evident transient outward potassium current (I to1) heterogeneity, and this heterogeneity is closely related to J point elevation, J wave formation, and some ventricular tachycardias such as ventricular fibrillations caused by Brugada syndrome. This study is designed to investigate transmural electrical heterogeneity of the canine right ventricle during repolarization (phase 1) from the viewpoint of 4-aminopyridine sensitive and calcium-independent I to1. Methods Adult canine single right ventricular epicardial (Epi) cells, mid-myocardial (M) cells, and endocardial (Endo) cells were enzymatically dissociated. Whole cell voltage-clamp recordings were made to compare the I to1 values of the three cell types. Results At 37℃ and using 0.2 Hz and +70 mV depolarizing test potentials, the average peak I to1 values of Epi cells and M cells averaged (4070±1720) pA and (3540±1840) pA, respectively. The activated and inactivated Epi and M cells kinetic processes were in accordance with the Boltzmann distribution. Compared with I to1 in Epi cells and M cells, the average peak I to1 in Endo cells was very low, averaged (470±130) pA. Conclusions These results suggest that there are evident differences and potent gradients in I to1 between the three cardiac cell types, especially between Epi and Endo cells. These differences are among the prominent manifestations of right ventricular electrical heterogeneity, and may form an important ionic basis and prerequisite for some malignant arrhythmias in the right ventricle, including those arising from Brugada syndrome and other diseases.展开更多
The purpose of the present study was to further study the characteristics and regulation of spontaneous transient outward currents(STOCs)in freshly isolated porcine coronary artery smooth muscle cells(ASMCs).STOCs wer...The purpose of the present study was to further study the characteristics and regulation of spontaneous transient outward currents(STOCs)in freshly isolated porcine coronary artery smooth muscle cells(ASMCs).STOCs were recorded using the perforated whole-cell patch-clamp configuration.STOCs were voltage-dependent and superimposed stochastically onto whole-cell Ca^(2+)-activated-K+(BKCa)currents.Charybdotoxin(ChTX,200 nmol/L),a selective blocker of BKCa channels,completely inhibited STOCs within 10 min.STOCs activity was greatly suppressed when extracellular Ca^(2+)concentration decreased from 1.8 mmol/L to 200 nmol/L,further removal of Ca^(2+)abolished STOCs activity.Ca^(2+)ionophore A23187(10μmol/L)increased STOCs activity significantly.Verapamil(20μmol/L)and CdCl2(200μmol/L),two kinds of organic L-type voltage-dependent Ca^(2+)channels(L-VDCCs)antagonists,had little effect on STOCs.In addition,the ryanodine receptors(RyRs)agonist caffeine(5 mmol/L)significantly activated STOCs.Application of ryanodine(50μmol/L)to block RyRs abolished STOCs,subsequent washout of ryanodine or application of caffeine failed to reproduce STOCs activity.Inhibition of inositol 1,4,5-trisphosphate receptors(IP_(3)Rs)by 2APB(40μmol/L)greatly suppressed the activity of STOCs,application of caffeine(5 mmol/L)in the presence of 2APB caused a burst of outward currents followed by inhibition of STOCs.These results suggest that STOCs in porcine coronary ASMCs are mediated by BKCa channels.Extracellular Ca^(2+)is essential for STOCs activity,while Ca^(2+)entry through L-VDCCs has little effect on STOCs.Intracellular Ca^(2+)release induced by RyRs is responsible for the regulation of STOCs,whereas IP_(3)Rs might also be involved.展开更多
Background Neural stem cells （NSCs） not only are essential to cell replacement therapy and transplantation in clinical settings, but also provide a unique model for the research into neurogenesis and epigenesis. How...Background Neural stem cells （NSCs） not only are essential to cell replacement therapy and transplantation in clinical settings, but also provide a unique model for the research into neurogenesis and epigenesis. However, little attention has been paid to the electrophysiological characterization of NSC development. This work aimed to identify whether the morphological neuronal differentiation process in NSCs included changes in the electrophysiological properties of transient A-type K^＋ currents （IA）. Methods NSCs were isolated from early postnatal rat hippocampus and were multiplied in basic serum-free medium containing basic fibroblast growth factor. Potassium currents were investigated and compared using whole-cell patch-clamp techniques and one-way analysis of variance （ANOVA）, respectively. Results Compared with NSC-derived neurons, cloned NSCs （cNSCs） had a more positive resting membrane potential, a higher input resistance, and a lower membrane capacitance. Part of cNSCs and NSC-derived neurons possessed both delayed-rectifier K^＋ currents （IDR） and IA, steady-state activation of IA in cNSCs （half-maximal activation at （21.34=L-4.37） mV） occurred at a more positive voltage than in NSC-derived neurons at 1-6 days in vitro （half-maximal activation at （12.85=L-4.19） mV）. Conclusions Our research revealed a developmental up-regulation of the IA component during differentiation of postnatal NSCs. Together with the marked developmental up-regulation of IDR in vitro neuronal differentiation we have previously found, the voltage-gated potassium channels may participate in neuronal maturation process.展开更多
文摘The transmural heterogeneous changes of transient outward potassium currents (Ito) in rabbit hypertrophic cardiaomyocytes and the effects of long-term prophylactic treatment with volsartan were investigated. Rabbits were divided into hypertrophy group (left ventricular hypertrophy induced by partial ligation of abdominal aorta), vol-treated group (volsartan was administrated after the ligation), and control group (sham operated). Myocytes were isolated by a two-step enzymatical method. The sub-endocardial (Endo) and sub-epicardium (Epi) tissues were separated from midmyocardium (Mid) with a razor. Whole-cell patch-clamp technique was used to record potassium currents. The results showed that membrane capacitance was larger in hypertrophic cells than those in control and vol-treated cells (P<0.01 vs control cells, n=30). The densities of Ito in hypertrophic cells were reduced by sub-epicardium (Epi) (27.8±2.9) %, midmyocardium (Mid) (41.0±4.7) %, and sub-endocardium (Endo) (20.3±3.4) % compared with those in control cells. The decrease of Ito density was more pronounced in Mid than in Epi and Endo (P<0.01 vs Epi or Endo). There were no significant differences in Ito densities between vol-treated group and control group in three layers separately. In conclusion, volsartan can inhibit the transmural heterogeneous changes of Ito in left ventricular hypertrophic cardiomyocytes in rabbit.
基金supported by the National Natural Science Foundation of China,No.31000514the Scientific Research Project for Talent with High Education of Xinxiang Medical University,No.2007502002
文摘The electrophysiological properties of potassium ion channels are regarded as a basic index for determining the functional differentiation of neural stem cells. In this study, neural stem cells from the hippocampus of newborn rats were induced to differentiate with neurotrophic growth factor, and the electrophysiological properties of the voltage-gated potassium ion channels were observed. Immunofluorescence staining showed that the rapidly proliferating neural stem cells formed spheres in vitro that expressed high levels of nestin. The differentiated neurons were shown to express neuron-specific enolase. Flow cytometric analysis revealed that the neural stem cells were actively dividing and the percentage of cells in the S ＋ G2/M phase was high. However, the ratio of cells in the S ＋ G2/M phase decreased obviously as differentiation proceeded. Whole-cell patch-clamp re- cordings revealed apparent changes in potassium ion currents as the neurons differentiated. The potassium ion currents consisted of one transient outward potassium ion current and one delayed rectifier potassium ion current, which were blocked by 4-aminopyridine and tetraethylammonium, respectively. The experimental findings indicate that neural stem cells from newborn rat hippo- campus could be cultured and induced to differentiate into functional neurons under defined condi- tions in vitro. The differentiated neurons expressed two types of outward potassium ion cur＇ents similar to those of mature neurons in vivo.
基金Supported by National Natural Science Foundation of China(No. 60674111)
文摘Acutely isolated mouse hippocampal CA3 pyramidal neurons were exposed to 3 mT static magnetic field,and the characteristics of transient outward K+ channel were studied using the whole-cell patch-clamp technique.The experiment revealed that the amplitude of transient outward potassium channel current was reduced.The maximum activated current densities of control group and exposure group were 163.62±20.68 pA/pF and 98.74±16.57 pA/pF(n=12,P<0.01) respectively.The static magnetic field exposure affected the activation and inactivation process of transient outward potassium channel current.Due to the magnetic field exposure,the half-activation voltage of the activation curves changed from 5.59±1.96 mV to 27.87±7.24 mV(n=12,P<0.05) ,and the slope factor changed from 19.43±2.11 mV to 25.87±4.22 mV(n=12,P<0.05) .The half-inactivation voltage of the inactivation curves also changed from-56.09±0.89 mV to-57.16±1.10 mV(n=12,P>0.05) and the slope factor of the inactivation curves from 8.69±0.80 mV to 10.87±1.02 mV(n=12,P<0.05) .The results show that the static magnetic field can change the characteristics of transient outward K+ channel,and affect the physiological functions of neurons.
文摘Mink相关蛋白1(MiRP1)是由KCNE基因家族成员KCNE2编码的具有一个跨膜结构的小分子蛋白质,发生在KCNE2上的相关突变能够引起遗传性长QT间期综合症(long QT syndrome,LQT6),但其机制不明.以往的工作表明,MiRP1调节瞬间外向钾电流(transient outward current,Ito)的功能,对维持心电稳定性具有重要的调节作用.在哺乳细胞系COS-7表达系统利用膜片钳全细胞记录方式,研究了两种LQT6相关的突变体I57T和V65M对Kv4.3通道功能的影响,从MiRP1对Ito功能调控的改变探讨LQT6引起心律失常的电生理机制.结果表明,KCNE2与Kv4.3共表达后对通道功能具有明显的调控作用,使通道的激活和失活明显减慢,电压依赖性失活发生正向移位,同时加快Kv4.3通道从失活中的恢复.I57T与Kv4.3共表达的通道,门控动力学以及通道的恢复特性更接近Kv4.3单独表达的通道,表现为丧失KCNE2的功能——"loss of function",而V65M的作用则与之刚好相反,对Kv4.3门控动力学和恢复特性的调节较KCNE2更强,同时,使通道电流密度明显降低,表现为增强KCNE2的功能——"gain of function".由此推论,KCNE2对Ito功能有重要的调节作用,发生在KCNE2基因上的突变,无论是增强(V65M)还是减弱(I57T)KCNE2的功能都可能通过改变Ito在心脏电稳定性中的贡献,从而使心脏在某些条件下发生心律失常.
文摘Background Some studies have confirmed that the right ventricular walls of most rodents, such as canines and humans, have evident transient outward potassium current (I to1) heterogeneity, and this heterogeneity is closely related to J point elevation, J wave formation, and some ventricular tachycardias such as ventricular fibrillations caused by Brugada syndrome. This study is designed to investigate transmural electrical heterogeneity of the canine right ventricle during repolarization (phase 1) from the viewpoint of 4-aminopyridine sensitive and calcium-independent I to1. Methods Adult canine single right ventricular epicardial (Epi) cells, mid-myocardial (M) cells, and endocardial (Endo) cells were enzymatically dissociated. Whole cell voltage-clamp recordings were made to compare the I to1 values of the three cell types. Results At 37℃ and using 0.2 Hz and +70 mV depolarizing test potentials, the average peak I to1 values of Epi cells and M cells averaged (4070±1720) pA and (3540±1840) pA, respectively. The activated and inactivated Epi and M cells kinetic processes were in accordance with the Boltzmann distribution. Compared with I to1 in Epi cells and M cells, the average peak I to1 in Endo cells was very low, averaged (470±130) pA. Conclusions These results suggest that there are evident differences and potent gradients in I to1 between the three cardiac cell types, especially between Epi and Endo cells. These differences are among the prominent manifestations of right ventricular electrical heterogeneity, and may form an important ionic basis and prerequisite for some malignant arrhythmias in the right ventricle, including those arising from Brugada syndrome and other diseases.
基金Supported by the National Natural Science Foundation of China (Grant No. 30370527)
文摘The purpose of the present study was to further study the characteristics and regulation of spontaneous transient outward currents(STOCs)in freshly isolated porcine coronary artery smooth muscle cells(ASMCs).STOCs were recorded using the perforated whole-cell patch-clamp configuration.STOCs were voltage-dependent and superimposed stochastically onto whole-cell Ca^(2+)-activated-K+(BKCa)currents.Charybdotoxin(ChTX,200 nmol/L),a selective blocker of BKCa channels,completely inhibited STOCs within 10 min.STOCs activity was greatly suppressed when extracellular Ca^(2+)concentration decreased from 1.8 mmol/L to 200 nmol/L,further removal of Ca^(2+)abolished STOCs activity.Ca^(2+)ionophore A23187(10μmol/L)increased STOCs activity significantly.Verapamil(20μmol/L)and CdCl2(200μmol/L),two kinds of organic L-type voltage-dependent Ca^(2+)channels(L-VDCCs)antagonists,had little effect on STOCs.In addition,the ryanodine receptors(RyRs)agonist caffeine(5 mmol/L)significantly activated STOCs.Application of ryanodine(50μmol/L)to block RyRs abolished STOCs,subsequent washout of ryanodine or application of caffeine failed to reproduce STOCs activity.Inhibition of inositol 1,4,5-trisphosphate receptors(IP_(3)Rs)by 2APB(40μmol/L)greatly suppressed the activity of STOCs,application of caffeine(5 mmol/L)in the presence of 2APB caused a burst of outward currents followed by inhibition of STOCs.These results suggest that STOCs in porcine coronary ASMCs are mediated by BKCa channels.Extracellular Ca^(2+)is essential for STOCs activity,while Ca^(2+)entry through L-VDCCs has little effect on STOCs.Intracellular Ca^(2+)release induced by RyRs is responsible for the regulation of STOCs,whereas IP_(3)Rs might also be involved.
基金This work was supported in part by grants from National Natural Science Foundation of China （No. 30971183）, Guangdong Natural Science Foundation （No. 7005213）, and Science and Technology Projects in Guangdong Province （No. 2009B030801230）.
文摘Background Neural stem cells （NSCs） not only are essential to cell replacement therapy and transplantation in clinical settings, but also provide a unique model for the research into neurogenesis and epigenesis. However, little attention has been paid to the electrophysiological characterization of NSC development. This work aimed to identify whether the morphological neuronal differentiation process in NSCs included changes in the electrophysiological properties of transient A-type K^＋ currents （IA）. Methods NSCs were isolated from early postnatal rat hippocampus and were multiplied in basic serum-free medium containing basic fibroblast growth factor. Potassium currents were investigated and compared using whole-cell patch-clamp techniques and one-way analysis of variance （ANOVA）, respectively. Results Compared with NSC-derived neurons, cloned NSCs （cNSCs） had a more positive resting membrane potential, a higher input resistance, and a lower membrane capacitance. Part of cNSCs and NSC-derived neurons possessed both delayed-rectifier K^＋ currents （IDR） and IA, steady-state activation of IA in cNSCs （half-maximal activation at （21.34=L-4.37） mV） occurred at a more positive voltage than in NSC-derived neurons at 1-6 days in vitro （half-maximal activation at （12.85=L-4.19） mV）. Conclusions Our research revealed a developmental up-regulation of the IA component during differentiation of postnatal NSCs. Together with the marked developmental up-regulation of IDR in vitro neuronal differentiation we have previously found, the voltage-gated potassium channels may participate in neuronal maturation process.
