Inhibitory effect of tetrahydropalmatine on calcium current in isolated cardiomyocyte of guinea pig.
OBJECTIVE
To study the effect of tetrahydropalmatine (THP) on calcium channels in ventricular single cells of guinea pig heart.


METHODS
Patch-clamp technique (whole cell recording) was used to observe calcium current in ventricular myocytes.


RESULTS
THP decreased ICa in ventricular myocytes with a dose and frequency-dependent manner. THP (0.1, 1, and 10 mumol.L-1) decreased ICa from 1.15 +/- 0.22, 0.91 +/- 0.18, and 1.60 +/- 0.42 nA (control) to 0.9 +/- 0.21 (P < 0.01), 0.56 +/- 0.21 (P < 0.01), and 0.83 +/- 0.21 nA (P < 0.05), respectively, number of cells is five in each group (n = 5), and the rates of the depression of ICa were 22%, 38%, and 48%, respectively. The effect was easily reduced by washing the cell with the Tyrode's solution. The current-voltage relation curve showed that the potential producing peak value of ICa was 0 mV at which THP had the most markedly inhibited action on ICa. When the stimulating frequency was changed, ICa varied in a frequency-dependent manner 5 min after THP was given, and the inhibition of THP was stronger at 2 Hz than that at 0.1 Hz.


CONCLUSIONS
THP possessed a Ca2+ channel blocking effect.
Xu
C
C
Department of Physiology, Harbin Medical University, China.
Sun
M Z
MZ
Li
Y R
YR
Yang
B F
BF
Wang
L J
LJ
Li
J M
JM
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001600:Berberine Alkaloids / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects*; D002478:Cells, Cultured; D006168:Guinea Pigs; D006352:Heart Ventricles; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques
D001600:Berberine Alkaloids; D002121:Calcium Channel Blockers; D015220:Calcium Channels; C014215:tetrahydropalmatine