Effect of ginsenosides on voltage-dependent Ca2+ channel subtypes in bovine chromaffin cells

In previous reports we have shown that ginsenosides inhibit high threshold voltage-dependent Ca2+ channels in neuronal cells. However, these studies did not show whether ginsenosides-induced inhibition of Ca2+ currents discriminates among the various Ca2+ channel subtypes, although it is known that there are at least five different Ca2+ channel subtypes in neuronal cells. In this study we investigated the effect of ginsenosides on high threshold voltage-dependent Ca2+ channel subtypes using their selective Ca2+ channel blockers nimodipine (L-type), omega -conotoxin GVIA (N-type), or omega -agatoxin IVA (P-type) in bovine chromaffin cells. We could observe that ginsenosides inhibited high threshold voltage-dependent Ca2+ currents in a dose-dependent manner. The IC50 was about 120 mug/ml. Nimodipine had no effect on ginsenosides response. However, the effect of ginsenosides on Ca2+ currents was reduced by w-conotoxin GVIA, omega -agatoxin IVA, and mixture of nimodipine, omega -conotoxin GVIA, and omega -agatoxin IVA. These data suggest that ginsenosides are negatively coupled to three types of calcium channels in bovine chromaffin cell, including an omega -conotoxin GVIA-sensitive (N-type) channel, an omega -agatoxin IVA-sensitive (P-type) channel and nimodipine/omega -conotoxin GVIA/omega -agatoxin VIA-resistant (presumptive Q-type) channel. Thus, the selective regulation of voltage-dependent Ca2+ subtypes by ginsenosides in bovine chromaffin cell could be the cellular basis of antistress effects induced by ginseng. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.