| Objectives:To investigate the antiarrhythmic mechanism of TMCC, we observed the effect of TMCC on sodium current (INa), L-type calcium current (Iea, L) and transient outward potassium current (Ito) in rat ventricular cardiomyocytes of arrhythmia induced by aconitine and ouabain.Methods:Enzymatic dissociation was used to get single rat ventricular myocytes and whole-cell patch clamp was used to record INa,lCa,L, Ito in normal and arrhythmic ventricular cardiomyocytes induced by aconitine and ouabain in rat exposed to amiodarone and different concentration of TMCC.Results:1. In normal ventricular cardiomyocytes of rat, TMCC (100,200,4001μmol·L-1) decreased INa densities from (45.56±1.96)pA/pF to (42.42±4.75)pA/pF,(39.71±1.63)pA/pF,(37.59±4.75)pA/pF(n=5, P<0.01), respectively. The inhibition was in a concentration-dependent manner.24.241μmol·L-1amiodarone decreased INa densities to (34.23±1.33)pA/pF (n=5, P<0.01). The INa Ⅰ-Ⅴ curves were shifted upwards by TMCC and amiodarone without changes of their active, peak and reverse potentials. TMCC and amiodarone turned INa steady-state activation and inactivation curves to right, which made activate and inactivate slowly.2. In arrhythmic ventricular cardiomyocytes induced by11μmol·L-1aconitine the INa density rised from (45.56±1.96) pA/pF to (59.19±11.49) pA/pF, TMCC (100,200,4001μmol·L-1) could inhibit the action by aconitine and made the Ⅰ-Ⅴ curves upper shift in a concentration-dependent manner. The INa densities were decreased to (51.61±5.96)pA/pF,(41.50±5.50)pA/pF,(40.91±6.73)pA/pF(n=5, P<0.01), respectively.24.241μmol·L-1amidodarone restored INa densities to (40.22±1.47)pA/pF (n=5, P<0.01).11μmol·L-1aconitine turned INa steady-state activation and inactivation curves to left, which made activate and inactivate quickly, TMCC and amiodarone can make them normal.3. In arrhythmic ventricular cardiomyocytes of rat induced by51μmol·L-1ouabain the INa density decreased from (45.56±1.96)pA/pF to(34.74±1.61)pA/pF(n=5, P<0.01), which was restored to (39.57.42±1.96)pA/pF,(36.61±2.47)pA/pF (32.95±1.18)pA/pF(n=5, P<0.01) by TMCC(100,200,400). The the INa density decreased to (28.47±1.65)pA/pF (n=5, P<0.01) by24.24μmol·L-1amiodarone. The Ⅰ-Ⅴ curves upward shift induced by5μmol·L-1ouabain was inhibited by TMCC(100,200μmol·L-1) while TMCC(400(μmol·L-1)and amiodarone made this shift further. INa steady-state activation and inactivation curves was shifted to the right by5μmol·L-1ouabain.4. In normal ventricular cardiomyocytes of rat, TMCC(100,200,400μmol·L-1) changed ICa, L densities from (-4.31±1.62)pA/pF to (4.02±0.75)pA/pF,(4.59±0.30)pA/pF,(5.17±0.20)pA/pF, respectively.400μmol·L-1TMCC increased ICa, L densities significantly(n=5, P<0.01).Amiodarone decreased ICa, L densities to (2.84±0.19)pA/pF(n=5, P<0.01). The ICa,Ⅱ-Ⅴ curves were shifted downwards by400μmol·L-1TMCC, while upwards by amiodarone.TMCC turned the ICa, L steady-state activation curves to left, while turned inactivation curves to right. Amiodarone turned the ICa. L steady-state activation curves to right, while turned inactivation curves to left..5. In arrhythmic ventricular cardiomyocytes induced by1μmol·L-1aconitine from (4.31±1.62)pA/pF to(6.40±1.92)pA/pF, TMCC(100,200,400μmol·L-1) could inhibit the action by aconitine and made the Ⅰ-Ⅴ curves upper shift in a concentration-dependent manner. The ICa, L densities were restored to (6.14±1.84)pA/pF,(5.65±1.69)pA/pF,(5.18±1.56)pA/pF(n=5, P<0.01), respectively.24.24μmol·L-1amidodarone restored ICa, L densities to (3.71±1.39)pA/pF (n=5, P<0.01).1μmol·L-1aconitine turned ICa.L steady-state activation curves to left, while inactivation curves to right. TMCC and amiodarone can make them normal.6. In arrhythmic ventricular cardiomyocytes induced by5μmol·L-1ouabain the current density decreased from (4.31±1.62) pA/pF to (2.89±0.52) pA/pF, TMCC (100,200,400μmol·L-1) could inhibit the action of ouabain and made the Ⅰ-Ⅴ curves upper shift in a concentration-dependent manner. The ICa, L densities were restored to (2.86±0.65)pA/pF,(3.87±0.57)pA/pF,(4.48±0.91)pA/pF(n=5, P<0.01), respectively.24.24μmol·L-1amidodarone restored ICa,L densities to (2.55±0.49)pA/pF (n=5, P<0.01).5μmol·L-1ouabain turned ICa. L steady-state activation curves to right, while inactivation curves to left. TMCC and amiodarone can make them normal.7. In normal ventricular cardiomyocytes of rat, the Ito density was concentration-dependently changed from (25.74±3.60)pA/pF to (21.95±2.11)pA/pF、(19.95±1.16)pA/pF、(18.87±1.27)pA/pF(n=5, P<0.01) by TMCC (100,200,400μmol-L-1), which was (17.364±1.20)pA/pF(n=5, P<0.01) by amiodarone. Both TMCC (100,200,400μmol·L-1) and amiodarone turned the Ito steady-state activation to the right, inactivation to the left.8. In arrhythmic ventricular cardiomyocytes induced by1μmol·L-1aconitine the Ito density was changed from (25.74±3.60)pA/pF to (17.29±1.50)pA/pF, which was restored to (18.09±1.38)pA/pF,(17.02±1.21)pA/pF,(16.88±1.18)pA/pF(n=5, P<0.01) and (17.364±1.20)pA/pF(n=5, P<0.01) by TMCC (100,200,400μmol·L-1) and24.24μmol·L-1amiodarone respectively. Both TMCC (100,200,400μmol·L-1) and amiodarone have little effect on the Itp steady-state activation and inactivation curves(n=5, P>0.05).9. In arrhythmic ventricular cardiomyocytes induced by5μmol·L-1ouabain the Ito density lowered to (17.75±1.96)pA/pF, which was changed to (18.70±2.75)pA/pF,(17.31±2.27)pA/pF,(16.78±1.81)pA/pF and (13.64±1.03)pA/pF(n=5, P<0.01)by TMCC (100,200,400μmol·L-1) and24.24μmol·L-1amiodarone respectively. Both TMCC (100,200,400μmol·L-1) had little effect on the Ito steady-state activation and inactivation curves(n=5,P>0.05)while amiodarone made.the activation curves shifted to the right further and the inactivation curves to the left further(n=5, P<0.05).Conclusion:1. TMCC inhibits INa in a concentration-dependent manner in normalcardiomyocytes, meanwhile, TMCC can restore INa to normal in ventricular cardiomyocytes.2. TMCC of lower concentration inhibits ICa, L which TMCC of high concentration inhances Iea. L in a biphasic manner in normal myocardiocytes.TMCC restores ICa. L in ventricular myocardiocytes.3. TMCC inhibits Ito in normal and abnormal myocardiocytes, in an use-dependent manner.4. Concerned with the effect on INa,Ica and Ito, TMCC is superior to amiodarone. |
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