Figure 3.

Ca²⁺ Responses of IC-21 cells to testosterone and testosterone-BSA. (A) A second or third addition of testosterone shortly after the first treatment induces a sustained increase in [Ca²⁺]_i rather than a Ca²⁺ spike. (B) Cells were treated for 4 min with testosterone and then for 2 min with EGTA before the second addition of testosterone that induced only a Ca²⁺ spike. (C) The first addition of testosterone-BSA induced a Ca²⁺ spike, whereas the second addition induced a sustained Ca²⁺ increase. (D) BSA alone had no effect on [Ca²⁺]_i (lower line). After incubation with testosterone-BSA for 2 min, cells were treated with EGTA before the second addition of testosterone-BSA. (E) After incubation of cells with testosterone-BSA, the cells were pretreated with both EGTA and U-73122 before the second addition of testosterone-BSA. (F) Cells were treated with pertussis toxin for 16 h (+ PTX) before adding testosterone-BSA. Arrows indicate addition of substances to IC-21 cells.