Figure 4. Identification of PLC isozymes involved in IP₃ generation in HeLa cells stimulated with histamine.

(A) Representative traces of IRIS-1 signal changes (ΔR/R₀; top) and Indo-5F signal changes (F/F₀; bottom) observed in thapsigargin-treated HeLa cells. The horizontal broken lines indicate the baseline levels. (B) Traces of the mean ± SD IRIS-1 signal changes (ΔR/R₀) observed in thapsigargin-treated HeLa cells after addition of 3 µM histamine (blue circles) or 3 µM histamine plus 2 mM Ca²⁺ (green circles). (C–F) Effects of PLC isozyme knockdown on the IP₃ increase evoked by 3 µM histamine alone (C), the IP₃ increase evoked by 2 mM Ca²⁺ alone (D), the first component of the IP₃ increase evoked by 3 µM histamine plus 2 mM Ca²⁺, and the second component of the IP₃ increase evoked by 3 µM histamine plus 2 mM Ca²⁺. Data are shown as means ± SD. The numbers of cells measured are shown in parentheses. Statistical analyses were performed by one-way ANOVA followed by Scheffe’s multiple comparison test. *P<0.05, **P<0.01, vs. the values in control siRNA-transfected cells.