ABSTRACT
This study aimed to investigate the underlying mechanism of Zhenwu Decoction in the treatment of heart failure by regulating electrical remodeling through the transient outward potassium current(I_(to))/voltage-gated potassium(Kv) channels. Five normal SD rats were intragastrically administered with Zhenwu Decoction granules to prepare drug-containing serum, and another seven normal SD rats received an equal amount of distilled water to prepare blank serum. H9c2 cardiomyocytes underwent conventional passage and were treated with angiotensin Ⅱ(AngⅡ) for 24 h. Subsequently, 2%, 4%, and 8% drug-containing serum, simvastatin(SIM), and BaCl_2 were used to interfere in H9c2 cardiomyocytes for 24 h. The cells were divided into a control group [N, 10% blank serum + 90% high-glucose DMEM(DMEM-H)], a model group(M, AngⅡ + 10% blank serum + 90% DMEM-H), a low-dose Zhenwu Decoction-containing serum group(Z1, AngⅡ + 2% drug-containing serum of Zhenwu Decoction + 8% blank serum + 90% DMEM-H), a medium-dose Zhenwu Decoction-containing serum group(Z2, AngⅡ + 4% drug-containing serum of Zhenwu Decoc-tion + 6% blank serum + 90% DMEM-H), a high-dose Zhenwu Decoction-containing serum group(Z3, AngⅡ + 8% drug-containing serum of Zhenwu Decoction + 2% blank serum + 90% DMEM-H), an inducer group(YD, AngⅡ + SIM + 10% blank serum + 90% DMEM-H), and an inhibitor group(YZ, AngⅡ + BaCl_2 + 10% blank serum + 90% DMEM-H). The content of ANP in cell extracts of each group was detected by ELISA. The relative mRNA expression levels of ANP, Kv1.4, Kv4.2, Kv4.3, DPP6, and KChIP2 were detected by real-time quantitative PCR. The protein expression of Kv1.4, Kv4.2, Kv4.3, DPP6, and KChIP2 was detected by Western blot. I_(to) was detected by the whole cell patch-clamp technique. The results showed that Zhenwu Decoction at low, medium, and high doses could effectively reduce the surface area of cardiomyocytes. Compared with the M group, the Z1, Z2, Z3, and YD groups showed decreased ANP content and mRNA level, increased protein and mRNA expression of Kv4.2, Kv4.3, DPP6, and KChIP2, and decreased protein and mRNA expression of Kv1.4, and the aforementioned changes were the most notable in the Z3 group. Compared with the N group, the Z1, Z2, and Z3 groups showed significantly increased peak current and current density of I_(to). The results indicate that Zhenwu Decoction can regulate myocardial remodeling and electrical remodeling by improving the expression trend of Kv1.4, Kv4.2, Kv4.3, KChIP2, and DPP6 proteins and inducing I_(to) to regulate Kv channels, which may be one of the mechanisms of Zhenwu Decoction in treating heart failure and related arrhythmias.
Subject(s)
Rats , Animals , Myocytes, Cardiac , Atrial Remodeling , Rats, Sprague-Dawley , Heart Failure/metabolism , RNA, Messenger/metabolism , PotassiumABSTRACT
OBJECTIVE@#To observe the effect of cinobufagin on transient outward potassium current () in rat dorsal root ganglion cells of cancer-induced bone pain (CIBP) and explore the possible analgesic mechanism of cinobufagin.@*METHODS@#Whole cell patch clamp technique was used to examine the effect of cionbufagin on in acutely isolated dorsal root ganglion (DRG) cells from normal SD rats and rats with bone cancer pain.@*RESULTS@#The DRG cells from rats with CIBP showed obviously decreased current density, an activation curve shift to the right, and an inactivation curve shift to the left. Cinobufagin treatment significantly increased the current density and reversed the changes in the activation and inactivation curves in the DRG cells.@*CONCLUSIONS@# current is decreased in DRG neurons from rats with CIBP. Cinobufagin can regulate the activation and inactivation of current in the DRG cells, which may be related to its analgesic mechanism.
Subject(s)
Animals , Rats , Analgesics , Pharmacology , Bufanolides , Pharmacology , Cancer Pain , Drug Therapy , Cells, Cultured , Ganglia, Spinal , Patch-Clamp Techniques , Potassium Channels , Metabolism , Rats, Sprague-DawleyABSTRACT
Objective To study the effect of allicin ( All) on potassium current in single atrial myocytes in rats. Methods Isolated rat atrial myocytes were isolated by perfusion and administered by extracellular perfusion method.Whole cell patch clamp technique was used to record transient outward potassium current ( Ito ) in atrial myocyte. Results In presence of 30 μmol·L-1 of All,the peak current of Ito was significantly reduced from (20.5±2.2) pA/pF to (11.3±2.1) pA/pF at+50 mV of test potential (P<0.01,n=12).This effect of All showed voltage- and concentration-dependence with IC50 of (19.0±2.5)μmol·L-1 .The steady-state activation curve of Ito was shifted to more positive potential and recovery time from inactivation was prolonged.In addition, they fail to find any effect of All on the steady-state inactivation and closed-state inactivation of Ito. Conclusion All can inhibit Ito by slowing down the process of activation and recovery from inactivation of channel.
ABSTRACT
Objective To study the effect of allicin ( All) on potassium current in single atrial myocytes in rats. Methods Isolated rat atrial myocytes were isolated by perfusion and administered by extracellular perfusion method.Whole cell patch clamp technique was used to record transient outward potassium current ( Ito ) in atrial myocyte. Results In presence of 30 μmol·L-1 of All,the peak current of Ito was significantly reduced from (20.5±2.2) pA/pF to (11.3±2.1) pA/pF at+50 mV of test potential (P<0.01,n=12).This effect of All showed voltage- and concentration-dependence with IC50 of (19.0±2.5)μmol·L-1 .The steady-state activation curve of Ito was shifted to more positive potential and recovery time from inactivation was prolonged.In addition, they fail to find any effect of All on the steady-state inactivation and closed-state inactivation of Ito. Conclusion All can inhibit Ito by slowing down the process of activation and recovery from inactivation of channel.
ABSTRACT
To investigate the effects of isovitexin Ⅳ on transient outward potassium current in rat ventricular myocytes. In this study, MTT assay was used to investigate the safe range of isovitexin. The results showed that the IC₅₀ of the drug was in the range of 10-30 μmol•L⁻¹, and the drug concentration of 1-3 μmol•L⁻¹ for the patch clamp test was within the safe range. In addition, the single ventricular myocytes were obtained by single-enzymatic hydrolysis through aortic retrograde perfusion. The transient outward potassium current (Ito) of rat ventricular myocytes was guided and measured by whole-cell patch-clamp technique and the changes of current characteristics were recorded after isovite was applied. When the concentration of IV was less than 0.1 μmol•L⁻¹, there was no significant effect on Ito. However, with the increase in the concentration of IV (≥0.3 μmol•L⁻¹), the peak of Ito was decreased gradually, from (32.32±2.9) pA/pF to （25.83±4.3） pA/pF, 1 μmol•L⁻¹ IV and (19.51±3.5) pA/pF, 3 μmol•L⁻¹ IV respectively, with an inhibition effect in a concentration-dependent manner. In the range of 1-3 μmol•L⁻¹, IV down-regulated the I-V curve of Ito significantly. The activation curve showed that IV can enable the maximum half activation potential (V1/2) to move to the positive direction, and the V1/2 was increased from (19.59±1.6) mV to (22.81±1.7) mV and (28.86±1.4) mV at concentration of 1, 3 μmol•L⁻¹, meanwhile the activation curve moved to the right. However, the maximum half inactivating potential (V1/2) of the steady-state inactivation curve of Ito was significantly decreased from (－51.43±0.99) mV to (－61.81±1.3) mV with concentration of 1 μmol•L⁻¹ and (－71.50±1.4) mV with concentration of 3 μmol•L⁻¹. The inactivation time constant of recovery from inactivation (τ) was up-regulated significantly from (94.89±0.73) ms to (118.5±1.5) ms and (162.4±1.4) ms at concentration of 1, 3 μmol•L⁻¹ respectively. Meanwhile IV could enable the inactivation recovery curve to move to the right, which suggested that it can prolong the recovery time from inactivation of the transient outward potassium channel. In conclusion, isovitexin had a high inhibitory effect on Ito in rat ventricular myocytes.
ABSTRACT
Voltage-gated ion channels play an important role in cell's excitability.HCN is short for hyperpolarization-activated cyclic nucleotide-gated channels, and Kv4 family is the main ingredients of transient outward potassium current (IA) produced by hippocampal neuron, both of which belong to voltage-gated ion channels.HCN channel and its mediated Ih current could influence the resting potential of cell membrane, control the excitability of neurons, synaptic potential and synaptic transmission.They also participate in cardiac pacing and rhythmic activity of some neurons.IA is the main ingredients of outward potassium current in the early period of action potential repolarization, which mainly takes part in regulating the synaptic input and counterpropagation of action potential.Kv4 channel could reduce the excitability of neurons.Studies indicate that mutations of these two channels lead to epilepsy.This article focuses on the structure、 distribution and function of HCN and Kv4 in epilepsy.
ABSTRACT
Objective To observe the impact of alone or combined use of ezetimibe and simvastatin on transient outward potassium current (Ito) in ventricular myocytes of rat model of ischemia and reperfusion (IR). Methods Seventy-five male SD rats were randomly divided into five groups, control group (CON), control-IR group (CIR), ezetimibe treatment group (EIR), simvastatin treatment group (SIR) and combined ezetimibe and simvastatin treatment group (ESIR). After two weeks of treat?ment with intragastic normal saline or drugs (ezetimibe or simvastatin), myocytes were isolated from right ventricular with colla?genaseⅡ, and Ito was recorded by whole-cell patch clamp technique. Results (1) The Ito current density at+60 mV was sig?nificantly decreased in CIR group than that of CON group (P0.05). The Ito current densities were higher in SIR group and ESIR group compared to those of CIR group. There was no significant difference in Ito current density between SIR group and ESIR group (P>0.05). (2) There was a significant increase in the half-inactivation (V1/2) in CIR group than that of CON group, but no significant differ?ence between EIR group and CIR group (P >0.05). There was a significant difference in the half-inactivation (V1/2) in SIR group and ESIR group compared to that of CIR group (P0.05). There was no significant difference in the slope factor (K) between five groups (P>0.05). (3) The time-con?stant (τ) of Ito recovery curves from inactivation was significantly higher in CIR group than that of CON group (P0.05). There was a significant difference in the time-con?stant (τ) of Ito recovery curves from inactivation in SIR group and ESIR group compared to that of CIR group (P0.05). Conclusion Simvastatin pre-treatment or ezetimibe+simvastatin pre-treatment can reverse the effect of IR on Ito of ventricular myocytes, but ezetimibe shows no such effects.
ABSTRACT
Objective: To observe the effect of cilostazol on the ion channel of right ventricular cells in experimental rats, and to explore the ion channel mechanism of ciolstazol for preventing the ventricular arrhythmia in Brugada syndrome. Methods: Our research was composed of 2 groups: ①Perfusion group, the cells were treated in 4 sub-groups by cilostazole at 1, 2, 5, 50μmol/L respectively, and there were 9, 5, 3, 7 cells were recorded at each sub-group to observe the differences of current density Ito at before and after treatment. ②Oral group, which included 4 sub-groups:Control 1 with 7 rats, Experiment 1 with 5 rats, and Control 2 with 8 rats, Experiment 2 with 6 rats respectively. The differences of current density Ito and ICa,L were studied between each Control and Experiment sub-groups. Results: In Perfusion group,①with cilostazole 1, 2, 5, 50μmol/L treatment, the current density Ito decreased in all sub-groups, when the self-command voltage at+60mV, the Ito was signiifcantly different in each sub-group at before and after treatment, all P0.05. In Oral group,①When the self-command voltage from-50mV reached the maximum of+60mV, the Ito was similar between Control 1 and Experiment 1 sub-groups, P>0.05.②When the self-command voltage at+10mV, the current density of ICa,L was slightly higher in Control 2 sub-group than that in Experiment 2 sub-group, P>0.05. Conclusion: Direct perfusion of cilostazole in right ventricular cells may inhibit Ito in experimental rats, such effect was similar with cilostazole treatment at (1-50)μmol/L. Cilostazole might prevent the ventricular arrhythmia in Brugada syndrome in experimental rats.
ABSTRACT
AIM: To determine the effect of exogenous phosphocreatine (PCr) at different concentrations on transient outward potassium (Ito) current in rat ischemic ventricular mid-myocardial (M) cells and to explore the antiarrhythmia mechanism in the treatment of ischemic heart disease. METHODS: M cells were isolated enzymatically from left ventricular mid-myocardium of rats. Peak Ito current was recorded by patch-clamp technique in the whole-cell configuration when M cells were superfused with normal Tyrode solution,simple ischemic solution,and simulated ischemic solution containing PCr at concentrations of 5,10,20 and 30 mmol/L for 10 min. RESULTS: Peak Ito current density of M cells superfused with simple simulated ischemic solution was significantly reduced by (76.1±6.3)% (P0.05). CONCLUSION: PCr reverses the inhibition of Ito current under ischemic condition in M cells,which may be the mechanism responsible for arrhythmia prevention in ischemic heart disease. PCr at concentrations of 0～10 mmol/L exerts significant dose-effect relationship.
ABSTRACT
AIM: To study the electrical heterogeneity of transient outward potassium current (I_(to)) in left and right ventricular myocytes of cardiomyopathy rat. METHODS: The rats were peritoneally injected with L-thyroxine 0.5 mg/kg for 10 d to establish the model of ventricular hypertrophy. The right and left ventricular parts of the heart were separated and the ventricular myocytes were prepared by step digestion using enzyme solution. I_(to) was recorded by using whole cell patch clamp technique. The change of the electrical heterogeneity was determined. RESULTS: The electrical heterogeneity of I_(to) existed in the normal myocytes of left and right ventricles. In the myocytes of left and right ventricles isolated from the cardiomyopathy rats, the electrical heterogeneity was enhanced obviously and showed statistical difference. At +40 mV depolarizing test potential, the current density of I_(to) in the myocytes of right ventricle was increased from (9.23±0.84) pA/pF to (11.19±1.73) pA/pF, while the current density of I_(to) in the myocytes of left ventricle was decreased from (6.99±1.14) pA/pF to (4.95 ±1.84) pA/pF and the dispersion was increased. The V_(1/2) of right ventricle steady inactivation was increased significantly [from (-68.85±1.37) mV to (-49.86±0.69) mV]. The time constant τ of de-inactivation changed significantly [τ left=(79.16±7.04) ms, τ right=(53.19±3.72) ms]. CONCLUSION: Enhanced electrical heterogeneity of I_(to) in the left and right ventricular myocytes of cardiomyopathy rat may represent one of the important ionic mechanisms for some arrhythmia caused by myocardial hypertrophy.
ABSTRACT
Objective To study the intervention effect of tanshinone on electrophysiological abnormality of hypertrophic cardicoyte in order to illuminate the underlying mechanism of tanshinone in preventing the arrhythmia induced by myocardial hypertrophy. Method Twenty-week-rid SD rats (200～250 g) were divided into 4 groups (8 in each group) randomly. Of 4 groups, rats of three groups were operated on by a procedure of 'one kidney one clamp' to make renal artery constriction. The rest group served as sham operation group (control group). When the blood pressure increased,rats of operation groups were divided into tanshinone group, captopril group and hyper-trophic group. The effects of tanshinoe and captopril were observed and compared on the action potential duration (APD),L-type calcium current (ICa, L) and transient outward potassium current (Ito) density in cellular membrane of hypertrophic myocardium by using patch clamp and intra-cellular calcium survey technique. Results The blood pressure in operation groups was obviously higher than that in sham-operation group (P<0.01), but there was no difference between operation groups (P>0.05). The ratio of ventricle weight to body weight (VW/BW) was much higher in hypertrophic group than in control group (P<0.01), and it significantly decreased after interven-tion with tanshinone or captopril (P<0.01). Compared with hypertrophic group, tanshinone markedly shortened the prolongation of action potential duration (P<0.01), decreased membrane capacity and peak amplitude of ICa,L(P<0.01), but had no effect on the density of ICa,L. Tanshinone also significantly increased Ito current density and peak amplitude, which were completely different from hypertrophic group (P<0.05). There were similar results foundin captopril intervention. Conclusions Tanshinone could reduce calcium influx and resume the activity of ho ion channels, and thus shorten the first phase and the plateau phase of repolarization and decrease the prolongation of APD in hypertrophic cadiocyte. So tanshinone can prevent the onset of arrhythmia attributed to the myocardial hypertrophy.
ABSTRACT
Objective To study the biological effect of ?3 adrenoceptor-activated electrophysiological activities in cardiac myocytes. Methods Changes of transient outward potassium ( Ito) and L-type calcium current ( ICa-L) in primary cultured guinea pig cardiacmyocytes were detected with the standard whole-cell patch clamp technique about 5 -10 min before and after administration of ?3 adrenoceptor agonist,4--2-hydroxy-( 3-chlorophenyl) ethyl-aminopropylphenoxyacetate ( BRL-37344; BRL). Results BRL could significantly increased the Ito in guinea pig cardiac myocytes with the I-V curve up-moved. When the membrane potential reached to + 80 mV,the density current increased from 6. 11 ? 1. 03 pA/pF to 8. 46 ? 2. 07 pA/pF ( n = 6,P =0. 013 064). BRL ( 10 -6mol/L) could significantly increase the ICa-Lin guinea pig cardiac myocytes,which was ( 2. 30 ?0. 75) -fold higher than in control group( n =5,P =0. 0063). When the membrane potential increased to + 10 mV ,the current,increased from 89. 25 ? 17. 83 pA to 205. 00 ? 72. 24 pA ( n = 5,P = 0. 006 3). Conclusion BRL-37344 can increase the transient Itoand ICa-L,thus further regulating the cardiac activities.
ABSTRACT
AIM: To study the current density of transient outward potassium current (I_(to)) in cells from the epicardial zone of the 1-week and 2-month infarcted rabbit heart. METHODS: Rabbits were infarcted by ligation of the left anterior descending coronary artery, 1 week as well as 2 months later, the single ventricular myocytes were isolated enzymatically from the infracted area of 1-week infracted rabbit heart (PMI-1 week) and 2-month infracted heart (PMI-2 months), region remote from the infracted zone of 2-month infracted heart (REM-2 months) and free wall of left ventricule from noninfarcted heart (CON). I_(to) was recorded using whole cell patch-clamp techniques. (RESULTS:) Membrane capacitance of myocytes in REM-2 months group was signifitantly larger than that in CON. I_(to)current density (at +60 mV) was significantly reduced in PMI-1 week [(7.5?2.4) pA/pF, n=12] and PMI-2 months [(10.6?4.1) pA/pF, n=18] compared with CON [(17.4?5.2) pA/pF, n=16], P
ABSTRACT
AIM: To study I_ to channel function in severe burn and its contribution to cardiac dysfunction induced by severe burn. METHODS: CHO-K1 cells were transfected with human Kv4.3, the major subunit of human I_ to channel. The expressed Kv4.3 channels were recorded by whole-cell patch clamp and the effects of rat burn serum on Kv4.3 current densities and kinetics were observed. RESULTS: Kv4.3 channels expressed in CHO-K1 cells were endowed with the characterization of fast activation and inactivation, which was quite similar to that of native I_ to channels in cardiomyocytes. Rat's burn serum at the concentration of 2% decreased the current density significantly. At +40 mV, the current density in control group was (67.6?15.1) pA/pF, in contrast to (32.3?9.7)pA/pF in burn serum-treated group (P