| Brucine is an alkaloid which is extracted from the seeds of the evergreen Joe Loganiaceae plants, it can eliminate stagnation and detumescence, alleviate pain, mainly remedy rheumatoid stubborn Bi paralysis and numbness, bruises, swelling carbuncle gangrene, modern clinical commonly used to treat rheumatoid arthritis, osteoporosis hyperplasia, sciatica, hemiplegia, polio sequelae, facial paralysis, myasthenia gravis, multiple neuritis and other diseases.In addition, many people also have been studied the role of brucine on the cardiovascular system. The results proved that the effect of brucine is to protect myocardial cells, anti-thrombosis, improve microcirculation blood flow and anti-arrhythmic. Previously it has been reported that brucine can concentration-dependently extend APD50, APD90 of fast action potential (FAP) and slow action potential (SAP) which was induced by high potassium depolarizing histamine and sodium chloride, significantly inhibited the APA, Vmax and Fc of the FAP and SAP, suggesting brucine may have blocked K+, Ca2+, Na+ channels in myocardial. The function of blocking calcium channels has been clearly, but the sodium, potassium channel role has not been reported. Although Li Minghua has reported the impact of brucine on the action potential, but no graphics above to facilitate analysis. The purpose of this experiment to re-do the action potential and further observing the impact on sodium, potassium channels and explore its antiarrhythmic mechanism.Action potential was recorded by the standard microelectrode technique in the papillary muscle of guinea pig ventricle. AP was elicited by a series of depolarizing pulse(1Hz , 2-4ms,2 times threshold).We recorded action potential amplitude(APA),action potential duration 50%(APD50),action potential duration 90%(APD90).We observed the effects of different does of brucine(3μmol/L,10μmol/L,30μmol/L) on AP parameters. Compared with control group, brucine 3μmol/L decreased the APA from(74.86±6.35)mv to(72.97±9.27)mv, there was no significant difference (p>0.05). Brucine 10μmol/L treatment group declined the APA action potential to (60.24±7.86) mv, there were significant differences (p<0.05). 30μmol/L treatment group declined APA action potential to (48.79±8.13) mv, the difference was significant (p<0.01).After washed out the APA recovered to (71.28±9.15) mv, compared with the control group there was no significant difference (p>0.05). Brucine 3μmol/L, 10μmol/L and 100μmol/L treatment groups prolonged the parameters of the action potential APD50, APD90 from the former administration (208.37±21.33) ms and (237.46±15.58) ms to the administration (219.74±19.97) ms and (254.12±18.62) ms, (230.83±20.38) ms and (267.97±22.15) ms ,(242.46±18.92) ms and (280.45±19.66) ms, the differences significantly (p<0.01).The action potential APD50, APD90 parameters resumed to (211.11±21.08) ms and (242.87±21.83) ms after elution, compared with the control group showed no significant difference (p>0.05). Brucine could extend the action potential APD50, APD90 in a dose-dependent manner of guinea pig papillary muscle, reduce action potential amplitude (APA).Whole-cell patch-clamp techniques were used to record the ionic currents of sodium in single cell of guinea pig ventricular myocytes (INa+), putting 0.1mM CdCl2 into extracellular fluid to block L-ICa2+ at the INa+ record, the holding potential was kept at -80mv, depolarizing from -80mv to +50mv, infantry band 10mv. Recording the sodium currents of the myocardial cells (negative control group) as a control, observing the impacts of different concentrations brucine 3μmol/L, 10μmol/L, 30μmol/L on INa+. The results show that compared with the negative control group, the negative control group and 3μmol/L does not affect the basic INa+ current peak; 10μmol/L can reduce the peak current of INa+ (p<0.05), 30μmol/L can reduce the peak current INa+ more significantly(p<0.01), inhibited in a dose- dependent manner. Through current-voltage curves, we can observe that in addition to decreasing the current amplitude, brucine did not affect the other parameters.The same method to record delayed rectifier K+ current (Ik+) in guinea pig ventricular myocytes by whole-cell patch-clamp technique, in accordance with the voltage activation settings of Ik+, the holding potential was kept at -80mv, the order voltage was from -40mv to +50 mv, each order voltage step is 10mv, sampling frequency is 0.25 KHz, the interval of stimulating is 15ms, the time course is 400 ms. Recording the delayed rectifier K+ currents(Ik+) of the myocardial cells (negative control group) as a control, observing the impacts of different concentrations brucine 3μmol/L, 10μmol/L, 30μmol/L on Ik+. The results showed that compared with the negative control group, the groups of 3μmol/L, 10μmol/L and 30μmol/L can reduce the peak current of Ik+ (p<0.01), inhibited in a dose-dependent manner. By observing current-voltage (I-V) curve,we can see that the curve was downward, but it does not affect the original voltage-dependent and time-dependent manner, and reduce the level of the test increased with the increasing voltage, a voltage-dependent changes.It turns out that: Firstly, brucine could prolong the course of APD50 and APD90 during the depolarization action potential duration in guinea pig papillary muscles, reduce the APA, showed in dose-dependent manner. Secondly, brucine can inhibit the peak current of INa+ on a single guinea pig ventricular myocytes in a concentration-dependent manner, and raise the I-V curve without paralleling movement, the curve shape was not changed. Thirdly, brucine can inhibit the peak current of Ik+ on a single guinea pig ventricular myocytes in a concentration-dependent manner, and raise the I-V curve without paralleling movement, the curve shape was not changed.
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