EFFECTS OF DEXAMETHASONE ON L-TYPE CALCIUM CURRENTS IN THE A7R5 SMOOTH MUSCLE-DERIVED CELL-LINE

Patch clamp experiments were used to characterize the effect of dexame thasone on calcium currents in A7r5 cells. Pretreatment for 48 h with 200 nM dexamethasone did not affect the single channel conductance, th e voltage dependence of channel opening, or the voltage-dependent inac tivation of L-type channels. However, dexamethasone caused an approxim ately 2-fold increase in the amplitude of L-type calcium currents in 5 out of 9 experiments, suggesting an increase in the number of active channels. The effect of dexamethasone appeared to be greatest on batch es of cells with low control current density. The amplitude of T-type calcium current was not affected by dexamethasone.