Effect of Gα
-coupled receptor activation upon surface expression of CXCR4 receptor, formyl peptide receptor, and VLA-4. U937 cells were treated with vehicle (untreated control), amthamine, isoproterenol, or sequentially with fMLFF, and vehicle (untreated control), amthamine or isoproterenol as described for experiments shown in Fig. 1 and 2. Next, cells were placed on ice and stained with anti-CXCR4 antibodies, A, anti-FPR antibodies, B, or CD49d antibodies, C. Histograms and bar graphs of mean channel fluorescence (MCF) ± SEM (n = 3) for unstained cell (autofluorescence), nonspecific binding (isotype control), treated with vehicle (untreated), and treated with different ligands are shown. One representative experiment out of two experiments is shown. * indicates means are not significantly different (P > 0.05) as calculated by one-way ANOVA analysis using GraphPad Prism software.