FIG. 3.

Ca²⁺ release in response to C5a and UTP in wild-type and Gα15^−/− macrophages. Changes in fluorescence over time in Fura-2-loaded wild-type and Gα15^−/− macrophages that responded to C5a were analyzed with the Felix program and reported as a ratio of optical density at 355 nm to optical density at 380 nm (OD355/OD380). Each tracing represents the average fluorescence changes of at least five individual cells. (A and B) Cells were exposed to C5a for 2 min and allowed to recover in the presence of Ca²⁺-free medium for 5 min. The cells were then exposed to UTP. (A) Wild-type cells; (B) Gα15^−/− cells; (C and D) wild-type (C) and Gα15^−/− (D) cells exposed to UTP for 2 min and washed with regular medium for a total of 15 min. Recording was stopped at 8 min to avoid photobleaching and restarted at 17 min prior to stimulation with C5a. Ca²⁺ release in the Gα15^−/− macrophages was blunted in response to C5a in both protocols, whereas the response to UTP was unchanged.