Effects of ginsenosides on Ca 2 channels and membrane capacitance in rat adrenal chromaffin cells

Abstract

We investigated the effects of ginseng total saponins (GTS) and five ginsenosides on voltage-dependent Ca 2+ channels and membrane capacitance using rat adrenal chromaffin cells. In this study, cells were voltage-clamped in a whole-cell recording mode and a perforated patch-clamp technique was used. The inward Ca 2+ currents (I Ca) was elicited by depolarization and the change in cell membrane capacitance (ΔC m) was monitored. The application of GTS (100 μg/ml) induced rapid and reversible inhibition of the Ca 2+ current by 38.8 ± 3.6% ( n = 16). To identify the particular single component that seems to be responsible for Ca 2+ current inhibition, the effects of five ginsenosides (ginsenoside Rb 1, Rc, Re, Rf, and Rg 1) on the Ca 2+ current were examined. The inhibitions to the Ca 2+ current by Rb 1, Rc, Re, Rf, and Rg 1 were 15.3 ± 2.2% ( n = 5); 36.9 ± 2.4% ( n = 7); 28.1 ± 1.9% ( n = 12); 19.0 ± 2.5% ( n = 10); and 16.3 ± 1.6% ( n = 15), respectively. The order of inhibitory potency (100 μM) was Rc > Re > Rf > Rg 1 > Rb 1. A software based phase detector technique was used to monitor membrane capacitance change (ΔC m). The application of GTS (100 μg/ml) induced inhibitory effects on ΔC m by 60.8 ± 9.7% ( n = 10). The inhibitions of membrane capacitance by Rb 1, Rc, Re, Rf, and Rg 1 were 35.3 ± 5.5% ( n = 7); 41.8 ± 7.0% ( n = 8); 40.5 ± 5.9% ( n = 9); 51.2 ± 7.6% ( n = 9); and 35.9 ± 5.1% ( n = 10), respectively. The inhibitory potencies of the ginsenosides on ΔC m were Rf > Rc > Re > Rg 1 > Rb 1. Therefore, we found that GTS and ginsenosides exerted inhibitory effects on both Ca 2+ currents and ΔC m in rat adrenal chromaffin cells. These results suggest that ginseng saponins regulate catecholamine secretion from adrenal chromaffin cells and this regulation could be the cellular basis of antistress effects induced by ginseng.