Tao Jin, Wang Hongyi, Chen Jiandong, Xu Huae, Li Shengnan
Department of Pharmacology, Nanjing Medical University, Nanjing 210029, China.
Am J Chin Med. 2005;33(5):797-806. doi: 10.1142/S0192415X05003417.
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 effect of DT-13 on L-type calcium currents (I(Ca,L)), exploring the mechanisms of DT-13's cardioprotective effects, we directly measured the I(Ca,L) in the adult rat cardiac myocytes exposed to DT-13 using standard whole-cell patch-clamp recording technique. Our results showed that DT-13 exerted inhibitory effects on the I(Ca,L) of the single adult rat cardiac myocytes. The current density was reduced by about 38% after exposure of the cells to DT-13 (0.1 microM) for 10 minutes, from the control value of 7.46 +/- 1.31 pA/pF to 4.25 +/- 0.35 pA/pF (n = 6, p < 0.05). This I(Ca,L)-inhibiting action of DT-13 was concentration-dependent. DT-13 up-shifted the current-voltage (I-V) curve, but did not significantly affect the half activation potential (V0.5). V0.5 was from -11.8 +/- 0.9 mV in the control to -12.6 +/- 1.9 mV in the presence of DT-13 at 0.1 micromol/L. DT-13 at 0.1 microM did not markedly affect the activation of I(Ca,L), but shifted the 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 dwarf lilyturf tuber and the inhibitory effects of DT-13 on L-type calcium currents.
麦冬皂苷单体13（DT - 13）是麦冬皂苷单体之一，已被发现具有强大的心脏保护作用。为了研究DT - 13对L型钙电流（I(Ca,L)）的影响，探索DT - 13心脏保护作用的机制，我们使用标准的全细胞膜片钳记录技术，直接测量了暴露于DT - 13的成年大鼠心肌细胞中的I(Ca,L)。我们的结果表明，DT - 13对单个成年大鼠心肌细胞的I(Ca,L)具有抑制作用。细胞暴露于DT - 13（0.1微摩尔/升）10分钟后，电流密度从对照值7.46±1.31皮安/皮法降低了约38%，降至4.25±0.35皮安/皮法（n = 6，p < 0.05）。DT - 13的这种I(Ca,L)抑制作用具有浓度依赖性。DT - 13使电流 - 电压（I - V）曲线向上移位，但对半数激活电位（V0.5）没有显著影响。V0.5在对照中为-11.8±0.9毫伏，在存在0.1微摩尔/升DT - 13时为-12.6±1.9毫伏。0.1微摩尔/升的DT - 13对I(Ca,L)的激活没有明显影响，但使I(Ca,L)的失活曲线向左移位。结合先前的报道，这些结果表明麦冬的心脏保护作用与DT - 13对L型钙电流的抑制作用之间可能存在密切关系。
