Effects of benzyltetrahydropalmatine on potassium currents in guinea pig and rat ventricular myocytes.
OBJECTIVE
To investigate the effects of benzyltetrahydropalmatine (BTHP) on rapidly activating component (I(Kr)), slowly activating component (I(Ks)) of delayed rectifier potassium current, inward rectifier potassium current (I(K1)), and transient outward potassium current (I(to)) in single ventricular myocytes.


METHODS
Whole-cell patch clamp technique was used to record ionic currents.


RESULTS
(1) BTHP 30 micromol/L reduced I(Kr) and I(Kr,tail) by 31 %+/-4 % and 36 %+/-5 % (n=6, P <0.01), respectively and inhibited I(Ks) and I(Ks,tail) by 40 %+/-6 % and 45 %+/-5 % (n=7, P <0.01), respectively. I(Kr) and I(Ks) were blocked by BTHP 1-100 micromol/L in a concentration-dependent fashion (IC50 value was 13.5 micromol/L and 95 % confidence limit: 11.2-15.8 micromol/L for I(Kr), 9.3 micromol/L and 95 % confidence limit: 7.8-11.8 micromol/L for I(Ks), respectively). (2) BTHP 5 micromol/L inhibited I(to) by 63 %+/-6 % (n=6, P <0.01). BTHP 1-100 micromol/L reduced I(to) in a concentration-dependent manner (IC50 value was 3.6 micromol/L and 95 % confidence limit: 2.9-4.3 micromol/L). (3) BTHP 200 micromol/L did not affect I(K1).


CONCLUSIONS
BTHP inhibited I(Kr), I(Ks), and I(to), but not I(K1). The antiarrhythmic effects of BTHP may be mainly due to its blockade on potassium channels.
Li
Yang
Y
Department of Cardiology, Tongji Hospital, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, China. liyang@hotmail.com
Fu
Li-Ying
LY
Yao
Wei-Xing
WX
Xia
Guo-Jin
GJ
Jiang
Ming-Xing
MX
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001600:Berberine Alkaloids / Q000494:pharmacology*; D002469:Cell Separation; D051668:Delayed Rectifier Potassium Channels; D005260:Female; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology; D008297:Male; D032383:Myocytes, Cardiac / Q000166:cytology / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects*; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects; D024642:Potassium Channels, Voltage-Gated; D051381:Rats; D017208:Rats, Wistar; D016276:Ventricular Function
D000889:Anti-Arrhythmia Agents; D001600:Berberine Alkaloids; D051668:Delayed Rectifier Potassium Channels; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D024642:Potassium Channels, Voltage-Gated; C059983:potassium channel protein I(sk); C060778:benzyltetrahydropalmatine