Inhibitory effect of tetrahydropalmatine on calcium current in isolated cardiomyocyte of guinea pig
Xu, C.; Sun, M.Z.; Li, Y.R.; Yang, B.F.; Wang, L.J.; Li, J.M.
Zhongguo Yao Li Xue Bao 17(4): 329-331
1996
ISSN/ISBN: 0253-9756 PMID: 9812715 Document Number: 457864
AIM: 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 I-Ca in ventricular myocytes with a dose and frequency-dependent manner. THP (0.1, 1, and 10 mu-mol cntdot L-1) decreased I-Ca from 1.15 +- 0.22, 0.91 +- 0.18, and 1.60 +- 0.42 nA (control) to 0.9 +-0.21 (P lt 0.01), 0.56+-0.21 (p lt 0.01), and 0.83+-0.21 nA (P lt 0.05), respectively, number of cells is five in each group (n = 5), and the rates of the depression of I-Ca 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 I-Ca was 0 mV at which THP had the most markedly inhibited action on I-Ca. When the stimulating frequency was changed, I-Ca 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. CONCLUSION: THP possessed a Ca-2+ channel blocking effect.