Inhibition of calmodulin abrogates fMLP- and SDF-1–induced LDV-FITC binding. (A) U937-FPR cells were pretreated with DMSO or W7 and stimulated at time 0 with Mn²⁺, buffer, fMLP, or SDF-1. LDV-FITC binding was analyzed in real time. One of 3 independent experiments is shown. (B) Ionomycin-induced pH changes in BCECF-loaded U937-FPR cells were determined using a fluorometer. Cells were pretreated with DMSO, ethylisopropyl amiloride (EIPA; 10 μM), a Na⁺/H⁺ exchange inhibitor, or W7 and stimulated with ionomycin at time 0.