EFFECTS OF GINSENOSIDES ON CA2+ CHANNELS AND MEMBRANE CAPACITANCE IN RAT ADRENAL CHROMAFFIN CELLS

We investigated the effects of ginseng total saponins (GTS) and five g insenosides on voltage-dependent Ca2+ channels and membrane capacitanc e using rat adrenal chromaffin cells. In this study, cells were voltag e-clamped in a whole-cell recording mode and a perforated patch-clamp technique was used, The inward Ca2+ currents (I-Ca) was elicited by de polarization and the change in cell membrane capacitance (Delta C-m) w as monitored. The application of GTS (100 mu g/ml) induced rapid and r eversible inhibition of the Ca2+ current by 38.8 +/- 3.6% (n = 16), To identify the particular single component that seems to be responsible for Ca2+ current inhibition, the effects of five ginsenosides (ginsen oside Rb,, Re, Re, Rf, and Rg(1)) on the Ca2+ current were examined. T he inhibitions to the Ca2+ current by Rb,, Re, 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 mu M) was Rc > Re > Rf > Rg(1) > Rb-1 . A software based phase detector technique was used to monitor membra ne capacitance change (Delta C-m). The application of GTS (100 mu g/ml ) induced inhibitory effects on Delta C-m by 60.8 +/- 9.7% (n = 10), T he inhibitions of membrane capacitance by Rb,, Rc, Re, Rf, and Rg(1) w ere 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. Th e inhibitory potencies of the ginsenosides on Delta C-m were Rf > Rc > Re > Rg(1) > Rb-1. Therefore, we found that GTS and ginsenosides exer ted inhibitory effects on both Ca2+ currents and Delta C-m in rat adre nal chromaffin cells. These results suggest that ginseng saponins regu late catecholamine secretion from adrenal chromaffin cells and this re gulation could be the cellular basis of antistress effects induced by ginseng. (C) 1998 Elsevier Science Inc.