[Electrophysiologic study of the biphasic effects of cyclovirobuxine D on arrhythmias].
OBJECTIVE
To explore the possible mechanism of cyclovirobuxine D (CVB-D) in countering and inducing arrhythmia, by way of studying its electro-physiological effect on ventricular papillary muscles of rats in vitro.


METHODS
The transmembrane potential of rat's isolated right ventricular papillary muscles were recorded using conventional glass micro-electrode technique.


RESULTS
(1) CVB-D in concentration of 13.3-63.3 micromol/L, showed prolonging effect on the action potential repolarization time, mainly the action potential duration 50 (APD50), APD70 and APD90, in dose-dependent manner, in concentration of 33.3-63.3 micromol/L, it could inhibit the resting potential, action potential amplitude (APA) and maximum depolarization velocity (Vmax) in dose-dependent manner. (2) CVB-D also showed time-dependent effect, the effect initiated 10 min after 20 micromol/L was perfused in ventricular muscle, the APD50, APD70 and APD90 were potentiated gradually along with prolongation of action time and reached the peak at 30-40 min, without any potentiation thereafter. (3) CVB-D could markedly prolong the effective refractory period (ERP) of action potential, increase the ratio of ERP/APD. (4) CVB-D in concentration of 33.3 micromol/L could induce frequent, multifocal spontaneous arrhythmia in some cells when the action time was longer than 45 min.


CONCLUSIONS
CVB-D has the action of anti-ventricular arrhythmia, the mechanism is correlated with the prolongation of APD and ERP of ventricular muscle as well as the increase of ERP/APD ratio, while it also has the effect of inducing arrhythmia, the mechanism might be concerned with excessive prolongation of APD and the inhibition on RP, APA and Vmax.
Chen
Zhang-qiang
ZQ
Department of Cardiology, The First Affiliated Hospital of Medical College, Zhejiang University, Hangzhou (310003).
Hu
Shen-jiang
SJ
Shi
Wei-ya
WY
Du
Juan
J
Shen
Yueliang
Y
Xia
Qiang
Q
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001145:Arrhythmias, Cardiac / Q000139:chemically induced* / Q000503:physiopathology; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D022062:Electrophysiologic Techniques, Cardiac; D006352:Heart Ventricles / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D032383:Myocytes, Cardiac / Q000166:cytology; D010210:Papillary Muscles / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012032:Refractory Period, Electrophysiological / Q000187:drug effects; D016276:Ventricular Function
D000889:Anti-Arrhythmia Agents; D004365:Drugs, Chinese Herbal; C032939:cyclovirobuxine D