Effect of dexamethasone on voltage-gated Ca2+ channels and cytosolic Ca2+ in rat chromaffin cells

THE present study examined whether the synthetic glucocorticoid dexamethasone (DEX) can modulate voltage-gated Ca channel (VGCC) activity, and as a consequence agonist-induced increases in cytosolic Ca, in cultured rat adrenal medullary chromaffin (RAMC) cells. Exposure to 1 μM DEX for 48 h significantly increased peak VGCC current (Δ +140%). DEX treatment also significantly potentiated the increases in cytosolic Ca in response to submaximal stimulatory concentrations of KCl (Δ +64%) and nicotine (Δ +32%). The Ca channel agonist BAY K-8644 increased both VGCC current (Δ+109%) and potentiated the KCl-stimulated increase in cytosolic Ca (Δ+35%) to a comparable extent to that seen with DEX. These data suggest that DEX treatment increases VGCC activity, and that this increased Ca influx leads to potentiation of agonist-induced increases in cytosolic Ca in RAMC cells.