Molecular Mechanisms of Large-Conductance Ca2+-Activated Potassium Channel Activation by Ginseng Gintonin
Figure 3
The signal transduction pathways in gintonin-mediated BKCa channel activation. ((a) and (b)) Time-current relationship following application of gintonin (10 μg/mL) or ginsenoside Rg3 (100 μM) for 30 s in the presence of U73122, an active PLC inhibitor, or U73343, an inactive PLC inhibitor, in oocytes expressing BKCa channels. Inset, the representative peak outward current amplitude at +40 mV from a holding potential of −80 mV was measured in the presence of gintonin or ginsenoside Rg3. The active or inactive PLC inhibitor was pretreated for 5 min before gintonin or ginsenoside Rg3 application. ((c) and (d)) Time-current relationship after application of gintonin (10 μg/mL) or ginsenoside Rg3 (100 μM) for 30 s in the presence of 2-APB, an IP3 receptor antagonist, or BAPTA, an intracellular Ca2+ chelator, in oocytes expressing BKCa channels. Inset, the representative peak outward current amplitude at +40 mV from a holding potential of −80 mV was measured in the presence of gintonin or ginsenoside Rg3. The application of 2-APB or BAPTA preceded the gintonin application by 2 h. (e) Summary histograms show the peak outward BKCa channel currents (mean ± S.E.M; -14 oocytes each) recorded in oocytes expressing the BKCa channel in the absence or presence of the indicated agents. (*, compared to gintonin alone).
