Figure 4. Effect of thapsigargin (TG) and induction of capacitative Ca²⁺ entry (A–C), and Ca²⁺ release from the internal Ca²⁺ store by ionomycin (D and E) in WT, M₃KO and M₁/M₃ double KO SMG cells.

Drugs were applied to the SMG cell suspension at the time point indicated by the arrow. A–C, [Ca²⁺]_i change in the nominal absence of external Ca²⁺ in response to 0.3 μm thapsigargin (black trace) or control dimethylsulfoxide (DMSO; grey trace) and that caused by addition of 2 mm Ca²⁺. Note the large [Ca²⁺]_i increase induced in all of the WT (A), M₃KO (B) and M₁/M₃ double KO (C) SMG cells by adding external Ca²⁺ following TG application (capacitative Ca²⁺ entry). D, [Ca²⁺]_i change in the absence of external Ca²⁺ in response to 10 μm ionomycin in the WT, M₃KO and M₁/M₃ double KO SMG cells. 1 mm EGTA was added to the external solution. E, summarized peak [Ca²⁺]_i increases induced by 10 μm ionomycin in WT, M₃KO, or M₁/M₃ double KO SMG cells (mean ± s.e.m.; n = 4 for each genotype). All the results shown are representative of 4 experiments.