A, RT-PCR detection of the transcripts of mouse formyl peptide receptors in neutrophils (PMN). The sizes of the individual transcripts, after PCR amplification, are indicated by the cDNA controls included in a parallel experiment. Data are representative of three separate experiments. B-D, Agonist-induced Ca2+ mobilization in RBL-mFPR1 cells (left panels) and RBL-mFPR2 cells (right panels) that were stimulated with WKYMVm (W-pep, B), fMIVIL (C), and fMIFL (D). All 3 peptides were used at 100 nM in assays using RBL-mFPR1. In assays using RBL-mFPR2, WKYMVm was used at 100 nM, and fMIVIL and fMIFL were each used at 1 μM. ATP, used in (B) to demonstrate equal loading of the fluorescent dye, was used at 1 μM. One representative set of tracings, from assays done on the same day, is presented out of a total of three separate experiments.