| Objective:To explore the effect of Nardosinone on the main ion channel currents(INa,Ito,ICa-L)and their kinetic characteristics in rat ventricular myocytes,so as to provide theoretical basis for the further development and utilization of Nardosinone.Methods:Single and free ventricular myocytes were isolated from the hearts of SD rats by single enzymolysis in vitro.The effects of different doses of Nardosinone on the current and kinetic characteristics of related ion channels in ventricular myocytes were observed by whole cell patch clamp technique.Results:1.Effects of Nardosinone on sodium ion current(INa)and its kinetic characteristics in rat ventricular myocytes(1)Effect of Nardosinone on sodium ion current(INa)in rat ventricular myocytesWe observed the effect of different concentrations of Nardosinone on INa by using acutely isolated rat ventricular myocytes.Resultsshowed that,1?mol/L of Nardosinone had no significant effect on INa.However,when the concentration increased to 3?mol/L,INa showed significant inhibition.With the increase of the concentration of Nardosinone,the effect of the drug on INa increased,showing significant concentration dependence.Among them,3,10and30?mol/L of Nardosinone decreased the peak sodium current from(-43.39±2.71)pA/pF before administration to(-32.81 ± 1.29)pA/pF,(-29.14±2.95)pA/pF and(-21.43± 1.04)pA/pF(P<0.01,n=6).(2)Effect of Nardosinone on ?-? curve of INaThe current voltage curve(?-? curve,the same below)oflNawas shifted up by 3,10,30?mol/L Nardosinone.However,the shape and trend of the curve hardly changed.(3)Effect ofNardosinone on INa activation curveThe activation curve was shifted to the right by 3,10,30?mol/L of Nardosinone,and half of the activation voltage(V1/2-ac)changed from(-52.86 ±5.21)mV to(-50.60 ±5.34)mV?(-47.83±3.73)mV and(-45.33±3.46)mV(P>0.05,n=6).The results showed that Nardosinone had no significant effect on the activation of INa(4)Effect of Nardosinone on INa inactivation curveThe inactivation curve of INa shifted to the hyperpolarized direction.3,10,30 ?mol/L of Nardosinone changed half of the inactivation voltage(V1/2-in)from(-52.22±2.79)mV before administration to(-65.57±3.36)mV(-74.36±6.78)mV and(-79.35±6.08)mV(P<0.01,n=6).k changed from(6.17±0.49)to(9.92 ±0.58),(10.29 ± 0.62)and(11.55 ± 0.82)before administration(P<0.01,n=6),Nardosinone significantly accelerated the inactivation ofINa.(5)Effect of Nardosinone on the recovery curve after INa inactivationThe recovery curve of INawas shifted to the right after inactivation,and the recovery time(?)oflNa changed from(14.76± 1.38)ms to(23.07± 1.51)ms,(33.80±1.54)ms and(46.66±2.85)ms(P<0.01,n=6),with the increase of the concentration of Nardosinone,the recovery time of INa from inactivation to activation prolonged.2.Effects of Nardosinone on transient outward potassium current(Ito)in rat ventricular myocytesand its kinetic characteristics in rat ventricular myocytes(1)Effect of Nardosinone on Ito of rat ventricular muscleWe continued to use acutely isolated rat ventricular myocytes to observe the effect of different concentrations of Nardosinone on Ito.When the drug was1 ?mol/L,Ito current had no significant change.However,when the concentration of Nardosinone reached more than 3?mol/L,the inhibition effect of Nardosinone on Itowas obvious.With the increase of the concentration of Nardosinone,the effect of the drug on Ito increased,showing a significant concentration dependence.The peak sodium current decreased from(38.65± 1.58)pA/pF before administration to(29.33±1.78)pA/pF,(21.11±1.66)pA/pF and(14.57±1.07)pA/pF(P<0.01,n=6).(2)Effect of Nardosinone on ?-? curve ofItoAfter administration of 3,10 and 30?mol/L of Nardosinone,the ?-? curve of Ito moved downward.However,the shape and trend of the curve hardly changed.(3)Effect ofNardosinone on Ito activation curve3,10,30 ?mol/L of Nardosinone could shift the activation curve of Ito to the right,and V1/2-ac changed from(14.96±0.74)mV to(26.39±1.15)mV,(32.63±1.27)mV,(36.73±1.63)mV(P<0.01,n=6).The results showed that the difficulty ofIto activation significantly increased.(4)Effect of Nardosinone on Ito inactivation curveAfter administration of 3,10 and 30?mol/L of Nardosinone,the steady-state inactivation curve of Ito shifted to the left,and V1/2-in changed from(-21.21±1.41)mV before administration to(-34.99± 1.56)mV,(-46.55± 1.60)mV and(-56.26± 1.48)mV(P<0.01,n=6),that is,Nardosinone could accelerate the inactivation of Ito.(5)Effect of Nardosinone on the recovery curve afterlto inactivationAfter administration of3,10 and 30?mol/L of Nardosinone,the recovery curve of Itoshifted to the right.?changed from(108.7±3.49)ms to(146.6±8.58)ms,(174.9±9.05)ms and(192.7±11.99)ms(P<0.01,n=6),suggestingthat different concentrations of Nardosinone could make the recovery curve shift to the right and prolonged the time from inactivation to activation.3.Effects of Nardosinone on L-type calcium channel current(ICa-L)and its kinetic characteristics in rat ventricular myocytes(1)Effects ofNardosinone on ICa-LWe then used the acutely isolated rat ventricular myocytes to observe the effect of different concentrations of Nardosinone on ICa-L.1 ?mol/L of Nardosinone had no significant effect on ICa-L,but when the concentration was increased to 3?mol/L,ICa-L showed a significant inhibitory effect.With the increase of the concentration of Nardosinone,the effect of the drug on ICa-L gradually increased,showing a significant concentration dependence.Among them,3,10,and 30?mol/L of Nardosinone reduced the peak current density of ICa-Ldecreased from(-22.93±2.35)pA/pF before administration to(-15.74±2.57)pA/pF,(-10.36± 1.72)pA/pF and(-7.60±1.09)pA/pF(P<0.01,n=6).the ICa-L current density was partially recovered after elution.(2)The effect of Nardosinone on the current voltage curve(I-V)ofICa-L3,10,30?mol/L Nardosinone could make the ?-? curve show an upward trend,However,the shape and trend of the curve hardly changed.(3)Effect of Nardosinone on the activation curve oflCa-L3,10,30?mol/L of Nardosinone could shift the activation curve of ICa-Lthe right.V1/2-acchanged from(-30.47±2.01)mV to(-17.17±1.47)mV,(-12.17±0.76)mV and(-6.87±0.59)mV(P<0.01,n=6),indicating that Nardosinone could increase the activation difficulty of ICa-L.(4)Effect of Nardosinone on the inactivation curve of ICa-L3,10 and 30 ?mol/L of Nardosinone could shift the steady-state inactivation curve of ICa-L to the left,and maked V1/2-in from(-22.72±0.82)mV before administration to(-36.53±0.87)mV,(-46.37± 1.53)mV and(-58.47± 1.92)mV(P<0.01,n=6),that is to say,Nardosinoneaccelerated the inactivation of ICa-L.(5)Effect of Nardosinone on recovery curve after inactivation of ICa-L3,10 and 30 ?mol/L of Nardosinone could shift the reactivation curve to the right and changed the recovery time ? from(19.12±2.29)ms to(31.71 ±2.70)ms,(40.77±3.85)ms and(50.85±4.57)ms(P<0.01,n=6),that is to say,the time for the drug to reactivate ICa-Lprolonged.Conclusion:The current and kinetic characteristics of the main ion channels(INa,Ito,ICa-L)in rat ventricular myocytes were affected by Nardosinone to varying degrees,which may be the mechanism of the antiarrhythmic effect of Nardosinone. |
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