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 Ca²⁺ channel (VGCC) activity, and as a consequence agonist-induced increases in cytosolic Ca²⁺, 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 Ca²⁺ in response to submaximal stimulatory concentrations of KCl (Δ +64%) and nicotine (Δ +32%). The Ca²⁺ channel agonist BAY K-8644 increased both VGCC current (Δ +109%) and potentiated the KCl-stimulated increase in cytosolic Ca²⁺ (Δ +35%) to a comparable extent to that seen with DEX. These data suggest that DEX treatment increases VGCC activity, and that this increased Ca²⁺ influx leads to potentiation of agonist-induced increases in cytosolic Ca⁺ in RAMC cells.