Effects of Chinese herbs on multiple ion channels in isolated ventricular myocytes.
BACKGROUND
Shensong Yangxin (SSYX) is one of the compound recipe of Chinese materia medica. This study was conducted to investigate the effects of SSYX on sodium current (I(Na)), L-type calcium current (I(Ca, L)), transient outward potassium current (I(to)), delayed rectifier current (I(K)), and inward rectifier potassium currents (I(K1)) in isolated ventricular myocytes.


METHODS
Whole cell patch-clamp technique was used to study ion channel currents in enzymatically isolated guinea pig or rat ventricular myocytes.


RESULTS
SSYX decreased peak I(Na) by (44.84 +/- 7.65)% from 27.21 +/- 5.35 to 14.88 +/- 2.75 pA/pF (n = 5, P < 0.05). The medicine significantly inhibited the I(Ca, L). At concentrations of 0.25, 0.50, and 1.00 g/100 ml, the peak I(Ca, L) was reduced by (19.22 +/- 1.10)%, (44.82 +/- 6.50)% and (50.69 +/- 5.64)%, respectively (n = 5, all P < 0.05). SSYX lifted the I - V curve of both I(Na) and I(Ca, L) without changing the threshold, peak and reversal potentials. At the concentration of 0.5%, the drug blocked the transient component of I(to) by 50.60% at membrane voltage of 60 mV and negatively shifted the inactive curve and delayed the recovery from channel inactivation. The tail current density of I(K) was decreased by (30.77 +/- 1.11)% (n = 5, P < 0.05) at membrane voltage of 50 mV after exposure to the medicine and the time-dependent activity of I(K) was also inhibited. Similar to the effect on I(K), the SSYX inhibited I(K1) by 33.10% at the test potential of -100 mV with little effect on reversal potential and the rectification property.


CONCLUSIONS
The experiments revealed that SSYX could block multiple ion channels such as I(Na) I(Ca, L), I(k), I(to) and I(K1), which may change the action potential duration and contribute to some of its antiarrhythmic effects.
Li
Ning
N
Center for Arrhythmia Diagnosis and Treatment, Fuwai Cardiovascular Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China.
Ma
Ke-Juan
KJ
Wu
Xiang-Feng
XF
Sun
Qi
Q
Zhang
Yi-Hui
YH
Pu
Jie-Lin
JL
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D006168:Guinea Pigs; D006352:Heart Ventricles; D007473:Ion Channels / Q000187:drug effects*; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects*; D015221:Potassium Channels / Q000187:drug effects; D051381:Rats; D015222:Sodium Channels / Q000187:drug effects
D000889:Anti-Arrhythmia Agents; D015220:Calcium Channels; D004365:Drugs, Chinese Herbal; D007473:Ion Channels; D015221:Potassium Channels; D015222:Sodium Channels