Fig. 6.

Involvement of Ca_v channels in Ca²⁺ influx induced by the intracellular store depletion. (A) Ca²⁺ leak from the intracellular pool is demonstrated by the reduction of TRH-induced [Ca²⁺]_i amplitude after ~6 min spent in Ca²⁺-deficient medium. (B) Returning Ca²⁺ to the extracellular medium after a shorter time (~ 2 min) induced smaller Ca²⁺ influx (black trace) that was inhibited by 1 μM nifedipine (gray trace). Notice the recovery of TRH-induced Ca²⁺ signal upon returning of Ca²⁺ to the medium. (C) Ca²⁺ influx induced by returning Ca²⁺ to the extracellular medium of cells with depleted pools by prolonged exposure to Ca²⁺-deficient medium and TRH (black trace) was partially inhibited by 1 μM nifedipine (gray trace). Experiments were done using Fura-2 as a Ca²⁺ indicator and traces shown are averages of at least 20 cells per experiment.