The Effects On Delayed Rectifier Potassium Of Normal And Hypertrophied Isolated Ventricular Myocytes Of Rats Intervened By The Volatile Oil Of Nardostachys Chinensis

Objective：To study the effects of the volatile oil of Nardostachys chinensis(VONC)on delayed rectifier potassium current in normal and hypertrophied isolatedventricular myocytes of rats．Including: dose-response curves, I-V curves, activation curves and inactivationcurves.Methods：1、Rat model of cardiac pressure overload: Abdominal aorta wasbanded by using microsurgical techniques to create cardiac pressure overload. Briefly,rat were anesthetized and the abdomen was opened. Then separate abdominal aortaand renal artery, ligate them with No.4needle. The procedure resulted in a transverseaortic banding of60-70%.2、4weeks after operation, use UCG to check the long axis section of theventriculus sinister、long axis section of the abdominal aorta、inter-ventricular septumthickness diastolic (IVSTd) and left ventricular posterior wall thickness diastolic(LVPWTd) of the rats.3、Rat was sacrificed after anesthesia with pentobarbital first. The heart wasquickly removed and hung on a Langendorff apparatus，and perfused initially withCa2+free Tyrode’S solution. Then perfused with enzymatic solution. As soon as theheart became softened，the ventricle muscle of rat was cut into nubs and blown withsucker in KB solution to obtain ventricular myocytes of rat.4、The whole-cell patch clamp was used to record Ikof normal and hypertrophiedventricular myocytes and dose-dependent curve,current-voltage curve, activatedcurve, inactivated curve to observe the change of currents of Ikcomparing effectswith different dose of the volatile oil of Nardostachys chinensis．Results：1. The effects of Ikintervened by Nardostachys chinensis in normal isolatedventricular myocytes1.1The volatile oil of Nardostachys chinensis reduced the current of Ikwithdose-dependent block relationship. At concentrations of1，3，5，10，20and50μg/g， the peak current of Ikwas respectively reduced(10.45±1.14)％，(20.18±2.54)％，(46.88±5.3)％，(78±9.2)％，（96±6.4）%and（98±5.6）%(n=5,P<0.05) at membranepotential of+50mV.1.2The current density of Ikwas impacted by the concentration at5μg/g of thevolatile oil of Nardostachys chinensis．The peak current density of Ikwas reduced to（5.18±0.33）pA/pF from (9.43±0.62mV)pA/pF (P<0.05, n=5)at membrane potentialof-90mV in5μg/g of the volatile oil of Nardostachys chinensis. It was reduced about45％．1.3The activation curve of Ikhas significant change in5μg/g of the volatile oilof Nardostachys chinensis. The50％of activation voltage of Ikwas to(23.65±0.65)mVfrom (28.19±0.57)mV (P<0.05, n=6); and slope was to (6.09±0.56)mV from(5.14±0.51)mV (P<0.05,n=6).1.4The inactivation curve of Ikhas significant change in5μg/g of the volatile oilof Nardostachys chinensis. The50％of inactivation voltage of Ikwas to (-82.84±1.27)mV from (-64.46±1.02)mV (n=6，P<0.05)and slope was to (14.40±1.03)mV from(13.35±1.064)mV (n=6, P<0.05).2. The effects of Ikintervened by Nardostachys chinensis in hypertrophiedisolated ventricular myocytes2.1The inhibition of the Ikcurrent in hypertrophied isolated ventricularmyocytes of rat after using the volatile oil of Nardostachys chinensis isdose-dependent block relationship；At concentrations of1，3，5，10，20and50μg/g，the peak current of Ikwas respectively reduced(2.52±0.34)％,(12.88±1.13)％,(16.58±2.32)％,(37.67±5.12)％,(47.58±6.64)%and (60.12±7.08)%(n=5,P<0.05)atmembrane potential of+50mV.2.2The current density of Ikin hypertrophied isolated ventricular myocytes wasimpacted by the concentration at5μ g/g of the volatile oil of Nardostachyschinensis． The peak current density of Ikwas reduced to(4.71±0.44)pA/pFfrom(5.64±0.38)pA/pF (n=5,P<0.05)at membrane potential of-90mV in5μg/g of thevolatile oil of Nardostachys chinensis．It was reduced about16.5％．2.3The activation curve of Ikhas significant change in5μg/g of the volatile oilof Nardostachys chinensis．The50％of activation voltage of Ikwas to(23.04±0.68)mV from(26.04±0.62)mV (P<0.05， n=6)； and slope was to （6.44±0.6） mV from(5.54±0.52)mV (n=6, P<0.05).2.4The inactivation curve of Ikhas significant change in5μg/g of the volatileoil of Nardostachys chinensis. The50％of inactivation voltage of Ikwasto(-75.92±1.72)mV from (-68.01±1.94)mV (n=6, P<0.05) and slope was to(15.26±1.95)mV from (12.34±1.56)mV (n=6,P<0.05).Conclusions：1. The inhibition of the Ikcurrent in isolated ventricular myocytes of rat afterusing the volatile oil of Nardostachys chinensis is dose-dependent block relationship；2. The I-V curve of Ikhas been moved down after using the volatile oil ofNardostachys chinensis；3. The activation curve of Ikshifts to the positive direction after using thevolatile oil of Nardostachys chinensis；4. The inactivation curve of Ikshifts to the negative direction after using thevolatile oil of Nardostachys chinensis.The volatile oil of Nardostachys chinensis blocks the current of Ik, which maychange the effective refractory period of ventricular myocytes of rat，and it maycontribute to some antiarrhythmic effects5. The inhibition of the Ikcurrent in hypertrophied isolated ventricular myocytesof rat after using the volatile oil of Nardostachys chinensis is dose-dependent blockrelationship；the I-V curve of Ikof hypertrophied isolated ventricular myocytes hasbeen moved down after using the volatile oil of Nardostachys chinensis；theactivation curve of Ikof hypertrophied isolated ventricular myocytes shifts to thepositive direction after using the volatile oil of Nardostachys chinensis； theinactivation curve of Ikof hypertrophied isolated ventricular myocytes shifts to thenegative direction after using the volatile oil of Nardostachys chinensis. But theeffects of Ikof hypertrophied isolated ventricular myocytes intervened byNardostachys chinensis were weaker than effects of normal isolated ventricularmyocytes intervened by Nardostachys chinensis.