The saponin monomer of dwarf lilyturf tuber, DT-13, reduces L-type calcium currents during hypoxia in adult rat ventricular myocytes.
The saponin monomer 13 of dwarf lilyturf tuber (DT-13), one of the saponin monomers of dwarf lilyturf tuber, has been found to have potent cardioprotective effects. In order to investigate the effects of DT-13 on L-type calcium currents (I(Ca,L)), exploring the mechanisms of DT-13's cardioprotective effects in the condition of pathophysiology, we directly measured the I(Ca,L) during hypoxia in the adult rat cardiac myocytes exposed to DT-13 using standard whole-cell patch-clamp recording technique. Our previous results showed that DT-13 exerted decreasing effects on the I(Ca,L) of the single adult rat cardiac myocytes. In the condition of hypoxia, the current density was inhibited by about 29% after exposure of the cells to DT-13 (0.1 micromol L(-1)) for 10 min, from 6.96+/-1.05 pA/pF to 4.38+/-0.35 pA/pF (n=5, P<0.05). This I(Ca,L)-inhibiting action of DT-13 was concentration-dependent and showed no frequency-dependence. DT-13 up-shifted the current-voltage (I-V) curve. Steady-state activation of I(Ca,L) was not affected markedly, and the half activation potential (V(0.5)) in the presence of DT-13 (0.1 micromol L(-1)) was also not significantly different. DT-13 at 0.1 micromol L(-1) markedly accelerated the voltage-dependent steady-state inactivation of calcium current and shifted the steady-state inactivation curve of I(Ca,L) to the left. In combination with previous reports, these results suggest that there might be a close relationship between the cardioprotective effects of DT-13 and L-type calcium channels in the condition of hypoxia.
Tao
Jin
J
Department of Pharmacology, Nanjing Medical University, Hanzhong Road 140, Nanjing 210029, PR China.
Wang
Hongyi
H
Zhou
Hong
H
Li
Shengnan
S
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000502:physiology*; D015687:Cell Hypoxia; D004305:Dose-Response Relationship, Drug; D005260:Female; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects*; D008297:Male; D008516:Medicine, Chinese Traditional; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D031441:Ophiopogon / Q000737:chemistry; D018408:Patch-Clamp Techniques; D028321:Plant Preparations / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012503:Saponins / Q000494:pharmacology*; D016276:Ventricular Function
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D028321:Plant Preparations; D012503:Saponins