FIGURE 5.

Histamine-evoked Ca²⁺ signals in WI-38 human lung fibroblasts do not involve Gα_i/o activation but require PLC and ER Ca²⁺ release. (A) Typical recording of the Ca²⁺ response to histamine (300 μM) in fibroblasts preincubated for 30 min with 100 ng/ml pertussis toxin (PT). (B) Mean ± SE of the peak amplitude of histamine-evoked Ca²⁺ transients in the absence (green bar) and presence of pertussis toxin (gray bar). Comparison between groups was performed using the Student’s t-test (ns = no statistically relevant differences between groups). (C) Typical recording of the effect of histamine (300 μM) on Ca²⁺ signal in cells pretreated for 15 min with U73122 (10 μM), a specific PLC inhibitor. (D) Typical recording of the Ca²⁺ response to histamine (300 μM) in cells pretreated for 15 min with U73343 (10 μM), an inactive analog of U73122. (E) Representative recording of the Ca²⁺ signal evoked by histamine (300 μM) in cells pretreated with CPA (10 μM) in the absence of extracellular Ca²⁺ (0Ca²⁺). (F) Mean ± SE of the peak Ca²⁺ response to histamine (300 μM; green bar) in the presence of U73122 10 μM (black bar), U73343 10 μM (blue bar) and CPA 10 μM (orange bar not visible, marked with a red arrow). The numbers in the figure represent the number of cells studied. Statistical comparison between groups was performed using ANOVA test (* = p ≤ 0.05).