The Effect Of Genistein On Ion Channels Of Rat Ventricular Myocytes

Objective:To investigate the effects of Cytisine on the several major ion channel currents(I_to,INa,I_Ca-L)and their kinetic characteristics in rat ventricular myocytes.Methods:ventricular myocardial cells were enzymatically isolated from SD rats by Langendorff with constant pressure and temperature.The whole-cell patch clamp techniques were used to observe the effects of different concentrations of Cytisine on the main channel currents(I_to,INa,I_Ca-L)in rat ventricular myocytes and the changes of kinetic characteristicsResults:1.Effect of Cy on sodium channel current（INa）in rat ventricular myocytesWe used acute isolated rat ventricular myocytes to observe the effect of Cy on INa.The results showed that:（1）Cy had an inhibitory effect on INa,and its inhibitory effect gradually increased with increasing concentration（≥100 μmol/L）,showing a significant concentration-dependence（500 μmol/L almost complete inhibited）.Among them,when the concentration of Cy was 100 μmol/L and 300 μmol/L,the peak sodium current on the cells was decreased from（-32.81 ±3.93）pA/pF to（-21.77±4.07）pA/pF and（-14.8±2.99）pA/pF（P<0.01 compared with the control group）.（2）The sodium current-voltage curve（I-V curve,the same below）is significantly shifted upward by 100 μmol/L and 300 μmol/L of Cy,but the activation potential,peak potential and reversal potential are hardly changed.（3）100μmol/L and 30μmol/L Cy can shift the sodium channel activation curve to the right and change the half-activation voltage V_1/2 from（-53.31±0.45）mV to（-50.59±0.34）mV and（-48.82±0.32）mV（P<0.05 compared with the control group）,that is,Cy can delay sodium channel activation.（4）100 μmol/L and 300 umol/L Cy can shift the sodium channel inactivation curve to the left and change the half-inactivation voltage V_1/2 from（-62.22±0.66）mV to（-70.46±0.56）mV and（-72.18±0.55）mV（P<0.05 compared with the control group）,that is,Cy can shift V_1/2 to hyperpolarization and accelerate inactivation.（5）100 μmol/L and 300 μmol/L Cy can make the recovery curve shift to the left after the sodium channel is inactivated,and change the recovery time τ from（21.79±0.72）ms to（23.56± 1.23）ms and（28.12±1.97）ms（P<0.05 compared with the control group）,that is,Cy significantly prolonged the recovery time after sodium channel inactivation.2.Effect of Cy on transient outward potassium current(I_to)in rat ventricular myocytesI_to was recorded and the effect of 10,30,100 μmol/L Cy on this current was observed.The results showed that:（1）Cy has an inhibitory effect on I_to.At a concentration lower than 10μmol/L,Cy has no significant effect on I_to,but with the increase of drug concentration（≥10 μM）,the I_to peak gradually decreases,Pre-dose（22.67± 1.57）pA/pF decreased to（17.91 ± 1.38）pA/pF,（15.62±1.65）pA/pF and（10.82±1.54）pA/pF（P<0.01 compared with the control group）,shown as concentration dependence.（2）With the increase of Cy concentration（≥30 μM）,the Ⅰ-Ⅴ curve of I_to was significantly shifted down,and then the trend of its trajectory did not change.（3）10,30,100μmol/L Cy can shift the I_to activation curve to the right and change the maximum half activation potential(V_1/2)from（21.56±0.27）mV to（24.26±0.67）mV,（25.65±0.82）mV and（39.03±1.22）mV（P<0.01 compared with the control group）,that is,Cy can delay the activation of I_to channel.（4）10,30,100μmol/L Cy can shift the steady state inactivation curve of I_to to the left,and the half inactivation potential(V_1/2)is changed from（-47.08± 1.85）mV before dosing to（-58.30±2.16）.mV,（-60.48±2.41）mV and（-70.01 ±3.46）mV（P<0.01 compared with the control group）,that is,Cy can shift V_1/2 to hyperpolarization and accelerate inactivation.（5）10,30,100 μmol/L Cy can make the recovery curve shift to the right after inactivation,and change the recovery time τ from（55.96±3.92）ms to（75.60±3.89）ms,（158.2±6.81）ms,and（214.2± 10.86）ms（P<0.01 compared with the control group）,suggesting that the recovery curve is shifted to the right when the concentration of Cy is 100 μmol/L,and the recovery time is greatly prolonged.3.Effect of Cy on L-type Ca²⁺current(I_Ca-L)in rat ventricular myocytesIca-L was recorded and the effect of 10,30,100 μmol/L Cy on this current was observed The results showed that:（1）Cy has an inhibitory effect on Ica-L.When concentration of the Cy was≥10μM the peak current density of Ica-L changed from（21.45± 1.27）pA/pF to（17.73± 1.48）pA/pF,（15.15±0.61）pA/pF and（10.67±0.51）pA/pF（P<0.01 compared with the control group）,current density of Ica-L after elution was not significantly different before and after administration,showing concentration dependence.（2）10,30,100 μmol/L Cy can shift the Ⅰ-Ⅴ curve upward and significantly inhibit the L-type calcium current,without changing the trend of its trajectory and reversal potential.（3）10,30,100μmol/L Cy can shift the activation curve of Ica-L to the right,and the half-activation voltage V_1/2 changes from（-23.07±0.11）mV to（-21.37±0.21）mV,（-20.19± 0.17）mV and（-19.17±0.13）mV（P<0.01 compared with the control group）,that is,Cy can delay channel activation.（4）10,30,100μmol/L Cy can shift the I_Ca-L steady-state inactivation curve to the left and change the half-activation voltage V_1/2 from（-45.15±1.93）mV before dosing to（-52.29±1.75）mV,（-62.50±1.87）mV and（-68.61±2.21）mV（P<0.01 compared with the control group）,that is,Cy can shift the inactivation curve to hyperpolarization and accelerate inactivation.（5）10,30,100μumol/L Cy can make the recovery curve shift to the right after inactivation,and change the recovery time τ from（11.58± 1.02）ms to（18.07± 1.35）ms,（21.90±1.64）ms and（34.88±2.67）ms（P<0.01 compared with the control group）,that is,Cy can prolong the calcium channel recovery time.Conclusion:Cytisine can directly block the main ion channels(INa,I_to and I_Ca-L)currents in rat ventricular myocytes,and can change their channel kinetic characteristics.