| Objective:To investigate the effect of Schisandrin B(SchB)on arrhythmia induced by aconitine in SD rats,and to explore the mechanism of its effect from the perspective of electrophysiology and ion channels.Methods:1.Guide the electrocardiogram(ECG)with standard lead ? and observe the effect of SchB on arrhythmia induced by aconitine in SD rats.2.Modified Langendorff device was used for reverse perfusion of isolated heart aorta,and ventricular myocytes from adult SD rats were obtained by single enzymatic hydrolysis at room temperature.3.Using the whole-cell patch-clamp technique to guide and record the currents of INa,Ito,and ICa-L,on ventricular myocyte membranes of rats before and after SchB,and observe their relationship to current density and current-voltage(?-?)Curve,activation curve,inactivation curve,recovery curve after inactivation.Results:1.Effect of SchB on arrhythmia induced by aconitine in SD ratsWe observed the effect of SchB on arrhythmia induced by aconitine in SD rats.The results show that:SchB at 20 mg/kg,40 mg/kg,and 80 mg/kg prolonged the occurrence time of arrhythmia in rats from(9.30±2.46)min before administration to(17.02±3.82)min,(23.52 ± 4.72)min,(29.32 ± 4.88)min(P<0.05);shortened the duration of arrhythmia in rats from(49.28 ± 4.89)min before administration to(38.53 ± 4.15)min,(30.65±3.15)min,(21.05 ± 3.05)min(P<0.05),that is,compared with the model group,SchB can prolong the occurrence of arrhythmia-induced various ventricular arrhythmias and shorten the duration of arrhythmias;in addition,SchB can reduce the occurrence of fibrillation significantly increased the survival rate of rats.Among them,the survival rates of SchB rats at 20 mg/kg,40 mg/kg,and 80 mg/kg were 30%,60%,and 80%.The survival rate of rats in the olive oil group(negative control)was 10%Control)was 10%(P<0.05).This shows that SchB has an antiarrhythmic effect caused by aconitine.2..Effects of different concentrations of SchB on currents of various ion channels in rat ventricular myocytes(1)The effect of SchB on sodium channel current(INa)in rat ventricular myocytesWe observed the effect of different concentrations of SchB on INa.The results show that:1,2,3,10,30,100 ?mol/L SchB can make the peak sodium current density(INa-Peak)from the pre-dose(-90.24 ± 6.93)pA/pF decreased to(-83.43 ± 5.32)pA/pF,(-79.67 ± 4.89)pA/pF,(-69.07± 6.17)pA/pF,(-62.48± 5.17)pA/pF,(-47.78± 3.69)pA/pF,(-18.69± 2.17)pA/pF.Among them,the changes in the data of the first two were not statistically significant(P>0.05,n=6),and the latter were statistically significant(P<0.01,n=6).This showsSchB has an inhibitory effect on INa,and this effect has a significant concentration dependence.Therefore,in subsequent experiments,we chose three concentrations of 3,10,and 30 ?mol/L to observe the effect of SchB on the kinetic characteristics of INa.The results showed that SchB can significantly increase the current-voltage(?-?)relationship curve of the INa,but the change trend and shapeof the ?-? curve have not changed;the INa activation curve was significantly shifted to the right,that is,it is going the polarization direction moves,and the half activation voltage(Vi/2-ac)changed from(-61.90±5.21)mV before administration to(-49.34±4.36)mV,(-43.69± 5.34)mV,(-37.80±3.23)mV(P<0.01,n=6),that is,SchB can increase the difficulty of channel opening.The effect of SchB on the mechanical process of INa steady-state inactivation.The data showed that SchB significantly shifted the INa inactivation curve to the left,that is,it moved to the direction of hyperpolarization,and maked half the inactivation voltage(V1/2-in)from(-46.80±6.21)mV before drug was changed to(-59.42±5.21)mV,(-71.16±6.45)mV,(-81.03 ±7.53)mV(P<0.01,n=6),changed slope factor k from(5.30 ± 0.49)before administration to(8.35±0.58),(9.19 ±0.62),(11.42± 0.82)(P<0.01,n=6),that is,SchB can accelerate the process of IN.steady-state inactivation.In addition,SchB also has an effect on the recovery kinetics after INa inactivation:3,10,30 ?mol/L SchB can shift the recovery curve to the right after inactivation of sodium channels,and make the recovery time ? from(14.68±1.72)ms becomes(30.73 ± 2.93)ms,(43.79 ± 3.87)ms,(47.68 ± 2.55)ms(P<0.01,n=6),that is,SchB can significantly prolong the recovery time after sodium channel inactivation.(2)Effect of SchB on transient outward potassium current(Ito)of rat ventricular myocytes SchB concentration of 1,2,3,10,30,100 ?mol/L maked the peak current density of rat ventricular cells Ito from(41.53± 2.67)pA/pF before administration reduced to(38.43 ±2.32)pA/pF,(37.17 ± 3.59)pA/pF,(26.01 ± 2.28)pA/pF,(22.31 ±1.84)pA/pF,(15.76 ±1.86)pA/pF,(11.95 ± 1.31)pA/pF(P<0.01,n=6),that is,SchB had no significant effect on Ito at concentrations below 2 ?mol/L(P>0.05,n=6),Statistically significant at 3 ?mol/L or greater(P<0.01,n=6),SchB had an inhibitory effect on Ito,and this effect had a significant concentration dependence.So we chosed three concentrations of SchB at 3,10 and 30?mol/L to study its effect on Ito kinetics.3 ?mol/L or more SchB significantly reduced the?-? curve of Ito,but the I-V curve's change trend and shape have not changed;SchB can shift the Ito activation curve to the right,3,10,30 ?mol/L SchB changed the half activation potential(V1/2-ac)from(14.56±0.47)mV before administration to(25.24± 0.59)mV,(32.35± 0.86)mV,(41.64±1.17)mV(P<0.01,n=6),that is,SchB can delay the activation of Ito channels;SchB shifts the Ito steady-state inactivation curve to the left,and 3,10,and 30?mol/L caused half of Ito inactivation potential(V1/2-in)changed from(-38.32±2.62)mV before dosing becomes(-51.13 ± 3.65)mV,(-63.31 ± 3.74)mV,(-71.26 ± 4.33)mV(P<0.01,n=6),that is,SchB moved V1/2-in to the direction of hyperpolarization and accelerate inactivation;3,10,30?mol/L SchB shifted the recovery curve to the right after inactivation,and maked the recovery time ? from(101.30±4.47)ms to(117.80±5.89)ms,(142.10±8.58)ms,(169.900±11.46)ms(P<0.01,n=6),suggesting that SchB can extend the recovery time.(3)Effect of SchB on L-type calcium channel current(ICa-L)of rat ventricular myocytesWe investigated the effects of 1,3,and 10 ?mol/L SchB on ICa-L current,and the results showed that SchB has an inhibitory effect on ICa-L,and this effect has a significant concentration dependence.Among them,after administration of 1,3,and 10 ?mol/L SchB,the peak current density of ICa-L changed from(-37.01 ± 2.12)pA/pF before administration to(-25.89 ± 1.56)pA/pF,(-20.02 ± 1.65)pA/pF and(-13.73 ± 1.11)pA/pF(P<0.01,n=6)),in addition,1,3,and 10 ?mol/L SchB shifted the ?-? curve of L-type calcium current up,but the ?-? curve's change trend and shape have not changed;the ICa-L activation curve was shifted to the right,and V1/2-ac changed from(-39.95±2.21)mV before administration to(-20.47 ± 1.31)mV,(-12.25 ± 0.23)mV and(-9.34 ± 0.13)mV(P<0.01,n=6)),that is,SchB can delay the activation of the channel;the ICa-L inactivation curve can be shifted to the left,and the half-inactivation voltagechanged from(-31.94±2.53)mV before dosing to(-45.51 ± 3.45)mV,(-54.02 ± 3.87)mV,and(-63.08±5.25)mV(P<0.01,n=6),That is,SchB moved the inactivation curve to the direction of hyperpolarization and accelerate inactivation;it shifted the recovery curve to the right after inactivation,and changed the recovery time ? value from(11.46 ± 1.32)ms to(24.66 ± 2.43)ms,(32.75±2.87)ms and(39.67±2.97)ms(P<0.01,n=6),that is,SchB can prolong the calcium channel recovery time.Conclusion:Schisandrin B has an antiarrhythmic effect caused by aconitine,and this effect is concentration-dependent and related to suppression of INa,Ito and ICa-L currents. |
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