Y.-H. Zhou’s scientific contributions

Aim: To investigate the effects of M3 receptor agonist choline on L-type calcium channels in guinea pig ventricular myocytes. Methods: Whole cell patch clamp technique was used to record L-type calcium current. Laser scanning confocal microscope ( LSCM ) was employed to measure the concentration of intracellular free calcium. Results: The application of 10 mmol · L-1 choline reduced the density of peak ICa-L from(9. 02 ± 0. 82) pA/pF to(5. 61 ± 0. 55) pA/pF (n = 4, P < 0. 01). ICa-L came back to (8. 12 ± 0. 65) pA/pF after the application of 5 nmol · L-1 4-DAMP. Choline remarkably shifted activation curve to the right, and delayed the voltage-dependent steady-state activation of calcium current. The half activation potential ( V1/2 ) was ( -18. 62 ± 1. 14 ) mV in the control and ( -21. 40 ± 1. 12) mV in the presence of choline 10 mmol · L-1 ( n = 6, P < 0. 05). Steady-state inactivation curve and the recovery time from inactivation were not affected markedly. LSCM recorded that KCl induced determined by used [ Ca 2+ ]i increasing could be depressed by choline ( 10 mmol · L-1 ) and the effect of choline could be blocked by 4-DAMP ( 5 nmol · L-1 ). Conclusion: Choline slows the activation procession of ICa-L and decreased [ Ca2+ ]i in ventricular myocytes will help its cardiac protection.

Aim: To investigate changes of M3 receptor-mediated delayed rectifier K current (IKM3) in atrial myocytes of canine models with persistent atrial fibrillation (AF) and normal dogs, and the effects of matrine on IKM3 to provide theoretical and experimental evidences for new target of drug therapy. Methods: AF models were established through rapid pacing. Whole-cell patch technique was used to record the current changes of atrial myocytes isolated from normal and AF model dogs and the drug effects were compared. Results: IKM3 density was significantly increased (232 ± 81 pA, n= 4) in canine atrial myocytes from persistent AF models compared with normal dogs (198 ± 80 pA, n = 4) at test potential of + 50 mV. The inhibitory effect of matrine on IKM3 was more potent in normal dogs than in AF model dogs. Conclusion: M3 receptor-mediated delayed rectifier K current (IKM3) might be the new therapeutic target in future AF treatment.

HERG/IKr plays an important role in repolarization of cardiac action potential. In pathological condition such as cardiac ischemia, congestive heart failure and myocardial hypertrophy, the density and kinetic properties of HERG/IKr will change. This review is about modulation of HERG/I Kr in pathological condition and effect of traditional chinese medicine on HERG/IKr.

AIM: To elucidate the possible antiarrhythmic mechanism of matrine. METHODS: Whole-cell patch-clamp technique was used to record ionic currents in ventricular myocytes. RESULTS: In guinea pig ventricular myocytes, matrine 100 μmol·L-1 prolonged 90% action potential duration (APD 90) by 40% at a stimulation of 0.1 Hz in a frequency-independent manner, inhibited IK1 by 47% at the test potential of - 120 mV, reduced IKr,tail by 50% and had no effect on IKs,tail. CONCLUSION: Matrine prolonged APD through blockade of multiple potassium currents, which may relate to its antiarrhythmic efficacy.

Aim: To investigate the effect of amiodarone on potassium currents in rat remodeling ventricular myocytes after myocardial infarction, and study the effect of amiodarone on electroremodeling after myocardial infarction. Methods: After hyperlipemia model in rat was set up by fat milk intragastric administration, left anterior descending coronary artery was ligated to set up acute myocardial infarction model. Whole cell patch clamp technique was used to record inwardly rectified potassium current (Ikl) and transient outward potassium current (Ito) in isolated rat ventricular myocytes of remodeling region. Results: Ikl of model group (-15.66 ± 1.40) PA/PF was significantly decreased compared with normal group (-21.02 ± 1.95) PA/PF (n = 4, P < 0.01), amiodarone group (-11.07 ± 1.11) PA/PF was obviously decreased than model group (n = 4, P < 0.05). Ito of model group (7.29 ± 1.02) PA/PF was significantly decreased than normal group (13.24 ± 1.16) PA/PF (n = 4, P < 0.01), amiodarone group(4.12 ± 1.01) PA/PF was obviously decreased than model group (n = 4, P < 0.05). Conclusion: It can be concluded that amiodarone can inhibit potassium currents in rat remodeling ventricular myocytes after myocardial infarction and affect repolarization.

AIM: To explore the cause of the weaker antiarrhythmic effects of matrine than that of E-4031, dofetilide and RP58866. METHODS: Whole-cell patch-clamp technique was used to record ionic currents in rabbit ventricular myocytes. RESULTS: 1 and 10 μmol · L-1 matrine did not affect the inward rectifier potassium current (Ikl). 50 and 100 μmol · L-1 matrine reduced Ikl by 6% (n = 8, P < 0.05) and 8% (n = 8, P < 0.05), respectively at test potential of -120 mV from holding potential of -70 mV. At -50 mV, Ikl decreased by 4% (n = 8, P < 0.05) and 8% (n = 8, P < 0.05). E-4031, dofetilide and RP58866 significantly inhibited Ikl. At test potential of -120 mV, 1 and 10 μmol · L-1 E-4031 decreased Ikl by 10% (n = 6, P < 0.05) and 45% (n = 6, P < 0.05). At -50 mV, Ikl was decreased by 5% (n = 8, P < 0.05) and 35% (n = 8, P < 0.05), respectively. 1 and 10 μmol · L-1 dofetilide decreased Ikl by 19% (n = 6, P < 0.05) and 25% at -120 mV. At -50 mV, Ikl was decreased by 11% (n = 6, P < 0.05) and 19% (n = 6, P < 0.05), respectively. At -120 mV, 1 μmol · L-1 and 10 μmol · L-1 RP58866 decreased Ikl by 21% (n = 8, P < 0.05) and 50% (n = 8, P < 0.05). At -50 mV, Ikl was decreased by 6% (n = 8, P < 0.05) and 11% (n = 8, P < 0.05), respectively. CONCLUSION: The lower efficacy and potency of matrine in the inhibitory effects on Ikl than that of E-4031, dofetilide and RP58866 is one of the reasons for weaker antiarrhythmic effects of the Chinese herb than that of pure compounds.

AIM: To investigate the antiarrhythmic mechanism of water extract from codyceps sinensis (CS) on transmembrane potassium currents in single ventricular myocyte of guinea pig and rat. METHODS: Whole-cell patch-clamp was used to record inward rectifier K+ current (IK1), delayed rectifier K+ current (IK) and transient outward K + current (Ito) in single ventricular myocyte of guinea pig and rat. RESULTS: In ventricular myocytes of guinea pig, IK1 was decreased from (-36.37±5.15) pA/pF to (-29.70±5.90) pA/pF (n=5, P<0.05) following CS 0.1 g · L-1 at -120 mV; Ik increased from (9.21±2.42) pA/pF to (11.54±2.98) pA/pF (n=6, P<0.01) at +70 mV. In rat, Ito was increased from (13.36±0.88) pA/pF to (16.48±1.09) (n=4, P<0.01). CONCLUSION: The antiarrythmic effects of codyceps sinensis may be related to potassium current. It increased IK and Ito, decreased I K1, resulting in APD decrease without early and delayed afterdepolarization.

AIM: To construct a new model based on cellular level in order to screen and evaluate effect of antiarrhythmic drugs. METHODS: Enzymatic dissociation was used to get single rat ventricular myocytes and whole cell patch-clamp techniques were used to record action potential (AP) and ionic currents such as sodium currents (INa), L-type calcium currents(ICa-L). Inward rectifier potassium currents(IK1) and transient outward potassium currents (Ito). RESULTS: Aconitine 1 μmol · L-1 prolonged the action potential duration at repolarization of 50% and 90%. The APD90 was significantly prolonged from (150. 23±7. 02) ms to (236. 03±23. 22) ms(n=8,P<0. 01). This prolongation was not recovered and further prolonged compared with aconitine 10 minutes after quinidine 10 micromole was administration (n=6?P<0. 05), whereas it was reversed by application of verapamil 10 micromole. Aconitine can increase inward sodium and L-type calcium current which could be inhibited by administration of verapamil. CONCLUSION: The single cellular action potential and many kinds of ionic currents were changed after exposure to aconitine. Any kinds of drugs which has antiarrhythmic effect may show treatment effects on the model. It provides a simple way to divide the types of antiarrhythmic drugs. So it is a stable and liable method to screen and evaluate antiarrhythmic drugs.