| Arrhythmia is a common clinical cardiovascular disease,many heart related diseases such as hypertension,myocardial infarction,heart failure and myocardial ischemia often associated with the occurrence of arrhythmia.Malignant arrhythmia such as ventricular tachycardia and ventricular fibrillation has a high mortality rate,which is a serious threat to peoples' health and life.These anti-arrhythmic drugs had single target but more adverse reactions which could lead to cardiac arrhythmias.Although with the development of modern medical technology,arrhythmia still is one of the difficult problems.Recent years,people gradually concentrated on traditional Chinese medicine,because traditional Chinese medicine adjust patients' physical condition and with multiple targets,multiple layers of advantage,as a treatment for arrhythmia classic prescription Zhigancao Decoction wins the favour of people.Confirmed by research that Zhigancao Decoction had obvious prevention and treatment on the arrhythmia patients,as well as a variety of drug-induced animal arrhythmia models.Generally considered that Zhigancao Decoction anti-arrhythma by extending the myocardial cell action potentials duration(APD).Futher study shown that Zhigancao Decoction could inhibit the L-type calcium current and transient outward potassium current(Ito),assuming that the extension of action potential is the result of many kinds of channel current comprehensive.Ikr which is the rapid component of the delayed rectifier potassium current,plays important roles in3 phase action potential.Inhibiting or promoting Ikr can extend or shorten action potentia.In myocardial cells,Ikr is formed by alpha subunit h ERG(Kv11.1)and auxiliary subunit KCNE1 or KCNE2(Mi RP2).In cardiomyocytes,native Ikr current is weak and it is difficult to separate it from other potassium current,so this study used the stably transfected HEK293 celllines expressing functional h ERG channels in order to discuss the influence of Zhigancao Decoction on electrophysiological characteristics of Ikr channel.This research to study effects of Zhigancao Decoction containing serum to the h ERG channel by patch clamp technique.In order to explain the mechanism of prescription anti-arrhythmic and to develope Chinese traditional medicine and modern research.Part 1 Effects of Zhigancao Decoction containing serum on actionPart 1 Effects of Zhigancao Decoction containing serum on action potential of ventricular myocytes in rabbit.Objective: To explore the effects of Zhigancao Decoction containing serum on AP in acute isolated rabbit ventricular myocytes.Methods: The decoction and concentration of Zhigancao Decoction were in accordance with traditional process.Took blood from rabbits after continuously intragastric administration in 5 days and got the Zhigancao Decoction containing serum and Drug-Free containing serum.The effects of different concentrations of Drug-Free containing serum and Zhigancao Decoction containing serum on the AP was compared by using perforated patch clamp technique.Results: Compared with the 0% Drug-Free containing serum,different concentrations of Drug-Free containing serum had no obvious effect on action potential(P>0.05),while the Zhigancao Decoction containing serum prolonged the APD in a concenration-dependent manner.Compared with pre-administration,5%,10%,20% and 40% of the Zhigancao Decoction containing serum extended APD50 by 14.17%,56.26%,44.61% and 87.06%respectively(P<0.01).APD90 extended by 10.07%,26.54%,45.86% and55.49% respectively(P<0.01).After washing,APD50 and APD90 could be partially restored,but did not reach the pre-drug level.Zhigancao Decoction containing serum had no effect on APA and Vmax(P>0.05).Conclusion: Zhigancao Decoction containing serum could extend action potential in a concentration-dependent manner in rabbits ventricular muscle cells.Part 2 The effects of Zhigancao Decoction containing serum on hERG channel.Objective: To observe the impact of h ERG current by perfusing Zhigancao Decoction containing serum,and to explain the change of the current from the channel dynamics.Methods: Whole cell patch clamp technique was used to record hERG current in stably transfected HEK293 cell lines expressing functional h ERG channels by perfusing different concentration of Drug-Free containing serum and Zhigancao Decoction rapidly.Results:(1)The influence of Drug-Free containing serum and Zhigancao Decoction containing serum on h ERG potassium current: The inhibitory was the highest when the 20% Zhigancao Decoction containing serum was given for 5 min,and the current could not be completely recovered after washing out.The inhibitory rates of 5%,10%,20%,40% Zhigancao Decoction containing serum on h ERG potassium currents were 15.73%,38.15%,46.73% and51.09% respectively(P<0.05).The IC50 was 15.47%.Drug-Free containing serum had no effect on h ERG potassium current.(2)The effect of Drug-Free containing serum and Zhigancao Decoction containing serum on h ERG potassium current: 5%-40% of Drug-Free containing serum had no effect on the current of h ERG potassium current,and 5%-40% serum reduced h ERG potassium current significantly.Compared with 0% Zhigancao Decoction containing serum,5%-40% Zhigancao Decoction containing serum moved the activation curve to the left side and reduced V1/2 from-13.21± 1.04 m V to-18.01 ± 0.62 m V,-17.84 ± 0.69 m V,-20.26 ± 0.52 m V,-20.70 ± 0.52 m V(P<0.05).(3)The effect of 20% Zhigancao Decoction containing serum on activation process: Zhigancao Decoction containing serum inhibited the activation process by extending the activation time constant(P<0.01)under the same activation voltage.(4)The effect of 20% Zhigancao Decoction containing serum on deactivation process: Zhigancao Decoction containing serum prolonged the deactivation process by extending the fast and slow deactivation time constant(P<0.01)under the same activation voltage.The effect could be partially but couldn't completely recovered after washing out.(5)The effect of 20% Zhigancao Decoction containing serum on steady-state inactivation process: The V1/2 increased 4.34 m V after giving 20% Zhigancao Decoction containing serum(P<0.01).The effect could be completely recovered after washing out(P<0.01).20% Zhigancao Decoction containing serum accelerated the steady-state inactivation process on h ERG potassium channels.(6)The effect of 20% Zhigancao Decoction containing serum on recovery from inactivation process: Zhigancao Decoction containing serum prolonged the recovery from inactivation process by extending the recovery from inactivation time constant(P<0.01)under the same activation voltage.The effect could be partially but couldn't completely recovered after washing out(P<0.01).Conclusions: The Zhigancao Decoction containing serum reduced hERG potassium current by accelerating h ERG channel inactivation,delaying h ERG channel activation,deactivation and recory from inactivation. |
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