Effects of Ginkgolide B on action potential and calcium, potassium current in guinea pig ventricular myocytes.
OBJECTIVE
To investigate the effect of Ginkgolide B (GB) on action potential (AP), delayed rectifier potassium current (IK), and L-type calcium current (I(Ca-L)) in guinea pig ventricular myocytes.


METHODS
Single ventricular myocytes were isolated by an enzymatic dissociation method. AP, IK, I(Ca-L) were recorded by whole-cell patch-clamp technique in either current or voltage clamp mode.


RESULTS
GB shortened APD in a concentration-dependent manner. GB 0.1, 1, and 10 micromol/L shortened APD50 by 7.9% (n=5, P>0.05), 18.4% (n=5, P<0.01), and 28.9% (n=6, P<0.01), respectively; APD90 by 12.4% (n=5, P>0.05), 17.6% (n=5, P<0.01), 26.4% (n=5, P<0.01), respectively. GB increased IK in a concentration-dependent manner. GB 0.1, 1, and 10 micromol/L increased IK by 20.1% (n=6, P<0.05), 43.1% (n=6, P<0.01), 55.6% (n=6, P<0.05); increased IK tail by 10.7% (n=6, P<0.05), 25.1% (n=6, P<0.05), and 37.7% (n=6, P<0.05), respectively at testing potential of +50 mV and shift the I-V curve of IK upward. But GB had no significant effect on I(Ca-L) at above concentrations.


CONCLUSIONS
GB significantly shortened APD in a concentration-dependent manner which mainly due to increase of IK.
Qi
Xiao-yan
XY
Department of Physiology, Shanghai University of Traditional Chinese medicine, Shanghai 200032, China.
Zhang
Zhi-xiong
ZX
Xu
You-qiu
YQ
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D051668:Delayed Rectifier Potassium Channels; D004224:Diterpenes / Q000302:isolation & purification / Q000494:pharmacology*; D020441:Ginkgo biloba / Q000737:chemistry; D046934:Ginkgolides; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology; D007783:Lactones / Q000302:isolation & purification / Q000494:pharmacology*; D008297:Male; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000502:physiology; D018408:Patch-Clamp Techniques; D010946:Plants, Medicinal / Q000737:chemistry; D015221:Potassium Channels / Q000187:drug effects*; D024642:Potassium Channels, Voltage-Gated
D020746:Calcium Channels, L-Type; D051668:Delayed Rectifier Potassium Channels; D004224:Diterpenes; D046934:Ginkgolides; D007783:Lactones; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; C045856:ginkgolide B; D002118:Calcium